html css java tutorial
TRANSCRIPT
1
HTML, CSS, JAVA SCRIPT
TUTORIAL
2
What is HTML?
HTML is a language for describing web pages.
HTML stands for Hyper Text Markup Language HTML is a markup language A markup language is a set of markup tags The tags describe document content HTML documents contain HTML tags and plain text HTML documents are also called web pages
HTML TagsHTML markup tags are usually called HTML tags
HTML tags are keywords (tag names) surrounded by angle brackets like <html> HTML tags normally come in pairs like <b> and </b> The first tag in a pair is the start tag, the second tag is the end tag The end tag is written like the start tag, with a forward slash before the tag name Start and end tags are also called opening tags and closing tags
<tagname>content</tagname>
HTML Elements"HTML tags" and "HTML elements" are often used to describe the same thing.
But strictly speaking, an HTML element is everything between the start tag and the end tag, including the tags:
HTML Element:
<p>This is a paragraph.</p>
Web BrowsersThe purpose of a web browser (such as Google Chrome, Internet Explorer, Firefox, Safari) is to read HTML documents and display them as web pages. The browser does not display the HTML tags, but uses the tags to interpret the content of the page:
3
HTML Page StructureBelow is a visualization of an HTML page structure:
<html> <body> <h1>This a Heading</h1>
<p>This is a paragraph.</p>
<p>This is another paragraph.</p>
</body>
</html>
HTML VersionsSince the early days of the web, there have been many versions of HTML:
Version YearHTML 1991HTML+ 1993HTML 2.0 1995HTML 3.2 1997HTML 4.01 1999XHTML 1.0 2000HTML5 2012XHTML5 2013
4
The <!DOCTYPE> DeclarationThe <!DOCTYPE> declaration helps the browser to display a web page correctly.
There are many different documents on the web, and a browser can only display an HTML page 100% correctly if it knows the HTML type and version used.
Common Declarations
HTML5
<!DOCTYPE html>
Writing HTML Using Notepad or TextEdit
Step 1: Start Notepad
To start Notepad go to:
Start All Programs Accessories Notepad
Step 2: Edit Your HTML with NotepadType your HTML code into your Notepad:
Step 3: Save Your HTML
5
Select Save as.. in Notepad's file menu.
When you save an HTML file, you can use either the .htm or the .html file extension. There is no difference, it is entirely up to you.
Save the file in a folder that is easy to remember, like w3schools.
Step 4: Run the HTML in Your BrowserStart your web browser and open your html file from the File, Open menu, or just browse the folder and double-click your HTML file.
The result should look much like this:
The HTML <head> ElementThe <head> element is a container for all the head elements. Elements inside <head> can include scripts, instruct the browser where to find style sheets, provide meta information, and more.
The following tags can be added to the head section: <title>, <style>, <meta>, <link>, <script>, <noscript>, and <base>.
6
The HTML <title> ElementThe <title> tag defines the title of the document.
The <title> element is required in all HTML/XHTML documents.
The <title> element:
defines a title in the browser toolbar provides a title for the page when it is added to favorites displays a title for the page in search-engine results
A simplified HTML document:
<!DOCTYPE html><html><head><title>Title of the document</title></head>
<body>The content of the document......</body>
</html>
HTML HeadingsHTML headings are defined with the <h1> to <h6> tags.
Example<h1>This is a heading</h1><h2>This is a heading</h2><h3>This is a heading</h3>
HTML ElementsAn HTML element is everything from the start tag to the end tag:
Start tag * Element content End tag *<p> This is a paragraph </p><a href="default.htm"> This is a link </a><br>
* The start tag is often called the opening tag. The end tag is often called the closing tag.
7
HTML Element Syntax An HTML element starts with a start tag / opening tag An HTML element ends with an end tag / closing tag The element content is everything between the start and the end tag Some HTML elements have empty content Empty elements are closed in the start tag Most HTML elements can have attributes
Don't Forget the End TagSome HTML elements might display correctly even if you forget the end tag:
<p>This is a paragraph<p>This is a paragraph
The example above works in most browsers, because the closing tag is considered optional.
Never rely on this. Many HTML elements will produce unexpected results and/or errors if you forget the end tag .
Empty HTML ElementsHTML elements with no content are called empty elements.
<br> is an empty element without a closing tag (the <br> tag defines a line break).
HTML Tip: Use Lowercase TagsHTML tags are not case sensitive: <P> means the same as <p>. Many web sites use uppercase HTML tags.
HTML Document Example<!DOCTYPE html><html>
<body><p>This is my first paragraph.</p></body>
</html>
8
The example above contains 3 HTML elements.
HTML Example ExplainedThe <p> element:
<p>This is my first paragraph.</p>
The <p> element defines a paragraph in the HTML document.The element has a start tag <p> and an end tag </p>.The element content is: This is my first paragraph.
The <body> element:
<body><p>This is my first paragraph.</p></body>
The <body> element defines the body of the HTML document.The element has a start tag <body> and an end tag </body>.The element content is another HTML element (a p element).
Styling HTML with CSSCSS was introduced together with HTML 4, to provide a better way to style HTML elements.
CSS can be added to HTML in the following ways:
Inline - using the style attribute in HTML elements Internal - using the <style> element in the <head> section External - using an external CSS file
The preferred way to add CSS to HTML, is to put CSS syntax in separate CSS files.
However, in this HTML tutorial we will introduce you to CSS using the style attribute. This is done to simplify the examples. It also makes it easier for you to edit the code and try it yourself.
Inline StylesAn inline style can be used if a unique style is to be applied to one single occurrence of an element.
To use inline styles, use the style attribute in the relevant tag. The style attribute can contain any CSS property. The example below shows how to change the text color and the left margin of a paragraph:
9
<p style="color:blue;margin-left:20px;">This is a paragraph.</p>
HTML Style Example - Background ColorThe background-color property defines the background color for an element:
Example<!DOCTYPE html><html>
<body style="background-color:yellow;"><h2 style="background-color:red;">This is a heading</h2><p style="background-color:green;">This is a paragraph.</p></body>
</html>
HTML Style Example - Font, Color and SizeThe font-family, color, and font-size properties defines the font, color, and size of the text in an element:
Example<!DOCTYPE html><html>
<body><h1 style="font-family:verdana;">A heading</h1><p style="font-family:arial;color:red;font-size:20px;">A paragraph.</p></body>
</html>
The font-family, color, and font-size properties make the old <font> tag obsolete.
10
HTML Style Example - Text AlignmentThe text-align property specifies the horizontal alignment of text in an element:
Example<!DOCTYPE html><html>
<body><h1 style="text-align:center;">Center-aligned heading</h1><p>This is a paragraph.</p></body>
</html>
The text-align property makes the old <center> tag obsolete.
Internal Style SheetAn internal style sheet can be used if one single document has a unique style. Internal styles are defined in the <head> section of an HTML page, by using the <style> tag, like this:
<head><style type="text/css">body {background-color:yellow;}p {color:blue;}</style></head>
HTML Style Tags
Tag Description<style> Defines style information for a document<link> Defines the relationship between a document and an external resource
Deprecated Tags and AttributesIn HTML 4, several tags and attributes were used to style documents. These tags are not supported in er versions of HTML.
11
Avoid using the elements: <font>, <center>, and <strike>, and the attributes: color and bgcolor.
HTML ParagraphsHTML paragraphs are defined with the <p> tag.
Example<p>This is a paragraph.</p><p>This is another paragraph.</p>
HTML LinksHTML links are defined with the <a> tag.
Example<a href="http://www.restarttechnologies.com">This is a link</a>
HTML Images - The <img> Tag and the Src Attribute In HTML, images are defined with the <img> tag.
The <img> tag is empty, which means that it contains attributes only, and has no closing tag.
To display an image on a page, you need to use the src attribute. Src stands for "source". The value of the src attribute is the URL of the image you want to display.
Syntax for defining an image:
<img src="url" alt="some_text">
The URL points to the location where the image is stored. An image named "boat.gif", located in the "images" directory on "www.w3schools.com" has the URL: http://www.w3schools.com/images/boat.gif.
The browser displays the image where the <img> tag occurs in the document. If you put an image tag between two paragraphs, the browser shows the first paragraph, then the image, and then the second paragraph.
HTML Images - The Alt AttributeThe required alt attribute specifies an alternate text for an image, if the image cannot be displayed.
12
The value of the alt attribute is an author-defined text:
<img src="boat.gif" alt="Big Boat">
The alt attribute provides alternative information for an image if a user for some reason cannot view it (because of slow connection, an error in the src attribute, or if the user uses a screen reader).
HTML Images - Set Height and Width of an ImageThe height and width attributes are used to specify the height and width of an image.
The attribute values are specified in pixels by default:
<img src="pulpit.jpg" alt="Pulpit rock" width="304" height="228">
Tip: It is a good practice to specify both the height and width attributes for an image. If these attributes are set, the space required for the image is reserved when the page is loaded. However, without these attributes, the browser does not know the size of the image. The effect will be that the page layout will change during loading (while the images load).
HTML Tables
Tables are defined with the <table> tag.
A table is divided into rows (with the <tr> tag), and each row is divided into data cells (with the <td> tag). td stands for "table data," and holds the content of a data cell. A <td> tag can contain text, links, images, lists, forms, other tables, etc.
Table Example<table border="1"><tr><td>row 1, cell 1</td><td>row 1, cell 2</td></tr><tr><td>row 2, cell 1</td><td>row 2, cell 2</td></tr></table>
How the HTML code above looks in a browser:
row 1, cell 1 row 1, cell 2row 2, cell 1 row 2, cell 2
13
HTML Tables and the Border AttributeIf you do not specify a border attribute, the table will be displayed without borders. Sometimes this can be useful, but most of the time, we want the borders to show.
To display a table with borders, specify the border attribute:
<table border="1"><tr><td>Row 1, cell 1</td><td>Row 1, cell 2</td></tr></table>
HTML Table HeadersHeader information in a table are defined with the <th> tag.
All major browsers display the text in the <th> element as bold and centered.
<table border="1"><tr><th>Header 1</th><th>Header 2</th></tr><tr><td>row 1, cell 1</td><td>row 1, cell 2</td></tr><tr><td>row 2, cell 1</td><td>row 2, cell 2</td></tr></table>
How the HTML code above looks in your browser:
Header 1 Header 2row 1, cell 1 row 1, cell 2row 2, cell 1 row 2, cell 2
14
The <html> element:
<html>
<body><p>This is my first paragraph.</p></body>
</html>
The <html> element defines the whole HTML document.The element has a start tag <html> and an end tag </html>.The element content is another HTML element (the body element).
HTML Attributes HTML elements can have attributes Attributes provide additional information about an element Attributes are always specified in the start tag Attributes come in name/value pairs like: name="value"
Attribute ExampleHTML links are defined with the <a> tag. The link address is specified in the href attribute:
Example<a href="http://www.restarttechnologies.com">This is a link</a>
HTML HeadingsHeadings are defined with the <h1> to <h6> tags.
<h1> defines the most important heading. <h6> defines the least important heading.
Example<h1>This is a heading</h1><h2>This is a heading</h2><h3>This is a heading</h3>
HTML Lines
15
The <hr>tag creates a horizontal line in an HTML page.
The hr element can be used to separate content:
Example<p>This is a paragraph</p><hr><p>This is a paragraph</p><hr><p>This is a paragraph</p>
HTML Line BreaksUse the <br> tag if you want a line break (a line) without starting a paragraph:
HTML Text Formatting TagsTag Description
<b> Defines bold text
<em> Defines emphasized text
<i> Defines a part of text in an alternate voice or mood
<small> Defines smaller text
<strong> Defines important text
<sub> Defines subscripted text
<sup> Defines superscripted text
<ins> Defines inserted text
<del> Defines deleted text
<pre> Defines pre formatted text
HTML CommentsComments can be inserted into the HTML code to make it more readable and understandable. Comments are ignored by the browser and are not displayed.
Comments are written like this:
Example<!-- This is a comment -->
16
17
HTML Tag ReferenceTag Description <p> Defines a paragraph <br> Inserts a single line break
HTML <col> TagExampleSet the background color of the three columns with the <colgroup> and <col> tags:
<table border="1"> <colgroup> <col span="2" style="background-color:red"> <col style="background-color:yellow"> </colgroup> <tr> <th>ISBN</th> <th>Title</th> <th>Price</th> </tr> <tr> <td>3476896</td> <td>My first HTML</td> <td>$53</td> </tr></table>
Definition and UsageThe <col> tag specifies column properties for each column within a <colgroup> element.
The <col> tag is useful for applying styles to entire columns, instead of repeating the styles for each cell, for each row.
HTML <thead> TagExampleAn HTML table with a <thead>, <tfoot>, and a <tbody> element:
<table border="1"> <thead> <tr> <th>Month</th>
18
<th>Savings</th> </tr> </thead> <tfoot> <tr> <td>Sum</td> <td>$180</td> </tr> </tfoot> <tbody> <tr> <td>January</td> <td>$100</td> </tr> <tr> <td>February</td> <td>$80</td> </tr> </tbody></table>
Definition and UsageThe <thead> tag is used to group header content in an HTML table.
The <thead> element is used in conjunction with the <tbody> and <tfoot> elements to specify each part of a table (header, body, footer).
Browsers can use these elements to enable scrolling of the table body independently of the header and footer. Also, when printing a large table that spans multiple pages, these elements can enable the table header and footer to be printed at the top and bottom of each page.
The <thead> tag must be used in the following context: As a child of a <table> element, after any <caption>, and <colgroup> elements, and before any <tbody>, <tfoot>, and <tr> elements.
HTML ListsThe most common HTML lists are ordered and unordered lists:
HTML Lists
An ordered list:
1. The first list item2. The second list item
An unordered list:
List item List item
19
3. The third list item List item
HTML Unordered ListsAn unordered list starts with the <ul> tag. Each list item starts with the <li> tag.
The list items are marked with bullets (typically small black circles).
<ul><li>Coffee</li><li>Milk</li></ul>
How the HTML code above looks in a browser:
Coffee Milk
HTML Ordered ListsAn ordered list starts with the <ol> tag. Each list item starts with the <li> tag.
The list items are marked with numbers.
<ol><li>Coffee</li><li>Milk</li></ol>
How the HTML code above looks in a browser:
1. Coffee2. Milk
HTML Definition ListsA definition list is a list of items, with a description of each item.
The <dl> tag defines a definition list.
The <dl> tag is used in conjunction with <dt> (defines the item in the list) and <dd> (describes the item in the list):
<dl><dt>Coffee</dt>
20
<dd>- black hot drink</dd><dt>Milk</dt><dd>- white cold drink</dd></dl>
How the HTML code above looks in a browser:
Coffee- black hot drinkMilk- white cold drink
HTML Block ElementsMost HTML elements are defined as block level elements or as inline elements.
Block level elements normally start (and end) with a line when displayed in a browser.
Examples: <h1>, <p>, <ul>, <table>
HTML Inline ElementsInline elements are normally displayed without starting a line.
Examples: <b>, <td>, <a>, <img>
The HTML <div> ElementThe HTML <div> element is a block level element that can be used as a container for grouping other HTML elements.
The <div> element has no special meaning. Except that, because it is a block level element, the browser will display a line break before and after it.
When used together with CSS, the <div> element can be used to set style attributes to large blocks of content.
Another common use of the <div> element, is for document layout. It replaces the "old way" of defining layout using tables. Using tables is not the correct use of the <table> element. The purpose of the <table> element is to display tabular data.
The HTML <span> Element
21
The HTML <span> element is an inline element that can be used as a container for text.
The <span> element has no special meaning.
When used together with CSS, the <span> element can be used to set style attributes to parts of the text.
HTML Grouping TagsTag Description
<div> Defines a section in a document (block-level)
<span> Defines a section in a document (inline)
HTML FormsHTML forms are used to pass data to a server.
An HTML form can contain input elements like text fields, checkboxes, radio-buttons, submit buttons and more. A form can also contain select lists, textarea, fieldset, legend, and label elements.
The <form> tag is used to create an HTML form:
<form>.input elements.</form>
HTML Forms - The Input ElementThe most important form element is the <input> element.
The <input> element is used to select user information.
An <input> element can vary in many ways, depending on the type attribute. An <input> element can be of type text field, checkbox, password, radio button, submit button, and more.
The most common input types are described below.
Text Fields
22
<input type="text"> defines a one-line input field that a user can enter text into:
<form>First name: <input type="text" name="firstname"><br>Last name: <input type="text" name="lastname"></form>
How the HTML code above looks in a browser:
First name:
Last name:
Note: The form itself is not visible. Also note that the default width of a text field is 20 characters.
Password Field<input type="password"> defines a password field:
<form>Password: <input type="password" name="pwd"></form>
How the HTML code above looks in a browser:
Password:
Note: The characters in a password field are masked (shown as asterisks or circles).
Radio Buttons<input type="radio"> defines a radio button. Radio buttons let a user select ONLY ONE of a limited number of choices:
<form><input type="radio" name="sex" value="male">Male<br><input type="radio" name="sex" value="female">Female</form>
How the HTML code above looks in a browser:
Male
Female
23
Checkboxes<input type="checkbox"> defines a checkbox. Checkboxes let a user select ZERO or MORE options of a limited number of choices.
<form><input type="checkbox" name="vehicle" value="Bike">I have a bike<br><input type="checkbox" name="vehicle" value="Car">I have a car </form>
How the HTML code above looks in a browser:
I have a bike
I have a car
Submit Button<input type="submit"> defines a submit button.
A submit button is used to send form data to a server. The data is sent to the page specified in the form's action attribute. The file defined in the action attribute usually does something with the received input:
<form name="input" action="html_form_action.asp" method="get">Username: <input type="text" name="user"><input type="submit" value="Submit"></form>
How the HTML code above looks in a browser:
Username:
If you type some characters in the text field above, and click the "Submit" button, the browser will send your input to a page called "html_form_action.asp". The page will show you the received input.
24
HTML EVENT ATTRIBUTES
Global Event AttributesHTML 4 added the ability to let events trigger actions in a browser, like starting a JavaScript when a user clicks on an element.
Below are the global event attributes that can be added to HTML elements to define event actions.
Window Event AttributesEvents triggered for the window object (applies to the <body> tag):
Attribute Value Description
onafterprint script Script to be run after the document is printed
onbeforeprint script Script to be run before the document is printed
onbeforeunload script Script to be run before the document is unloaded
onerror script Script to be run when an error occur
onhaschange script Script to be run when the document has changed
onload script Fires after the page is finished loading
onmessage script Script to be run when the message is triggered
onoffline script Script to be run when the document goes offline
ononline script Script to be run when the document comes online
onpagehide script Script to be run when the window is hidden
onpageshow script Script to be run when the window becomes visible
onpopstate script Script to be run when the window's history changes
onredo script Script to be run when the document performs a redo
onresize script Fires when the browser window is resized
onstorage script Script to be run when a Web Storage area is updated
onundo script Script to be run when the document performs an undo
onunload script Fires once a page has unloaded (or the browser window has been closed)
25
Form EventsEvents triggered by actions inside a HTML form (applies to almost all HTML elements, but is most used in form elements):
Attribute Value Description
onblur script Fires the moment that the element loses focus
onchange script Fires the moment when the value of the element is changed
oncontextmenu script Script to be run when a context menu is triggered
onfocus script Fires the moment when the element gets focus
onformchange script Script to be run when a form changes
onforminput script Script to be run when a form gets user input
oninput script Script to be run when an element gets user input
oninvalid script Script to be run when an element is invalid
onreset script Fires when the Reset button in a form is clickedNot supported in HTML5
onselect script Fires after some text has been selected in an element
onsubmit script Fires when a form is submitted
Keyboard EventsAttribute Value Description
onkeydown script Fires when a user is pressing a key
onkeypress script Fires when a user presses a key
onkeyup script Fires when a user releases a key
Mouse EventsEvents triggered by a mouse, or similar user actions:
Attribute Value Description
onclick script Fires on a mouse click on the element
26
ondblclick script Fires on a mouse double-click on the element
ondrag script Script to be run when an element is dragged
ondragend script Script to be run at the end of a drag operation
ondragenter script Script to be run when an element has been dragged to a valid drop target
ondragleave script Script to be run when an element leaves a valid drop target
ondragover script Script to be run when an element is being dragged over a valid drop target
ondragstart script Script to be run at the start of a drag operation
ondrop script Script to be run when dragged element is being dropped
onmousedown script Fires when a mouse button is pressed down on an element
onmousemove script Fires when the mouse pointer moves over an element
onmouseout script Fires when the mouse pointer moves out of an element
onmouseover script Fires when the mouse pointer moves over an element
onmouseup script Fires when a mouse button is released over an element
onmousewheel script Script to be run when the mouse wheel is being rotated
onscroll script Script to be run when an element's scrollbar is being scrolled
27
CSSCSS stands for C ascading S tyle S heets
Styles define how to display HTML elements Styles were added to HTML 4.0 to solve a problem External Style Sheets can save a lot of work External Style Sheets are stored in CSS files
CSS DemoAn HTML document can be displayed with different styles:
Styles Solved a Big ProblemHTML was never intended to contain tags for formatting a document.
HTML was intended to define the content of a document, like:
<h1>This is a heading</h1>
<p>This is a paragraph.</p>
When tags like <font>, and color attributes were added to the HTML 3.2 specification, it started a nightmare for web developers. Development of large web sites, where fonts and color information were added to every single page, became a long and expensive process.
To solve this problem, the World Wide Web Consortium (W3C) created CSS.
In HTML 4.0, all formatting could be removed from the HTML document, and stored in a separate CSS file.
All browsers support CSS today.
CSS Saves a Lot of Work!CSS defines HOW HTML elements are to be displayed.
Styles are normally saved in external .css files. External style sheets enable you to change the appearance and layout of all the pages in a Web site, just by editing one single file!
28
CSS SyntaxA CSS rule has two main parts: a selector, and one or more declarations:
The selector is normally the HTML element you want to style.
Each declaration consists of a property and a value.
The property is the style attribute you want to change. Each property has a value.
CSS ExampleA CSS declaration always ends with a semicolon, and declaration groups are surrounded by curly brackets: p {color:red;text-align:center;} To make the CSS more readable, you can put one declaration on each line, like this:
Examplep{color:red;text-align:center;}
CSS CommentsComments are used to explain your code, and may help you when you edit the source code at a later date. Comments are ignored by browsers.
A CSS comment begins with "/*", and ends with "*/", like this:
/*This is a comment*/p{text-align:center;/*This is another comment*/color:black;font-family:arial;}
29
CSS Id and Class The id and class SelectorsIn addition to setting a style for a HTML element, CSS allows you to specify your own selectors called "id" and "class".
The id SelectorThe id selector is used to specify a style for a single, unique element.The id selector uses the id attribute of the HTML element, and is defined with a "#".The style rule below will be applied to the element with id="para1":
Example#para1{text-align:center;color:red;}
The class SelectorThe class selector is used to specify a style for a group of elements. Unlike the id selector, the class selector is most often used on several elements.
This allows you to set a particular style for many HTML elements with the same class.
The class selector uses the HTML class attribute, and is defined with a "."
In the example below, all HTML elements with class="center" will be center-aligned:
Example.center {text-align:center;} You can also specify that only specific HTML elements should be affected by a class.
In the example below, all p elements with class="center" will be center-aligned:
Examplep.center {text-align:center;}
30
CSS Background CSS background properties are used to define the background effects of an element.
CSS properties used for background effects:
background-color background-image background-repeat background-attachment background-position
Background ColorThe background-color property specifies the background color of an element.
The background color of a page is defined in the body selector:
Examplebody {background-color:#b0c4de;} With CSS, a color is most often specified by:
a HEX value - like "#ff0000" an RGB value - like "rgb(255,0,0)" a color name - like "red"
In the example below, the h1, p, and div elements have different background colors:
Exampleh1 {background-color:#6495ed;}p {background-color:#e0ffff;}div {background-color:#b0c4de;}
Background ImageThe background-image property specifies an image to use as the background of an element. By default, the image is repeated so it covers the entire element. The background image for a page can be set like this:
Examplebody {background-image:url('paper.gif');} Below is an example of a bad combination of text and background image. The text is almost not readable:
31
Examplebody {background-image:url('bgdesert.jpg');}
Background Image - Repeat Horizontally or VerticallyBy default, the background-image property repeats an image both horizontally and vertically. Some images should be repeated only horizontally or vertically, or they will look strange, like this:
Examplebody{background-image:url('gradient2.png');} If the image is repeated only horizontally (repeat-x), the background will look better:
Examplebody{background-image:url('gradient2.png');background-repeat:repeat-x;}
Background Image - Set position and no-repeatWhen using a background image, use an image that does not disturb the text. Showing the image only once is specified by the background-repeat property:
Examplebody{background-image:url('img_tree.png');background-repeat:no-repeat;} In the example above, the background image is shown in the same place as the text. We want to change the position of the image, so that it does not disturb the text too much. The position of the image is specified by the background-position property:
Examplebody{background-image:url('img_tree.png');background-repeat:no-repeat;
32
background-position:right top;}
Background - Shorthand propertyAs you can see from the examples above, there are many properties to consider when dealing with backgrounds. To shorten the code, it is also possible to specify all the properties in one single property. This is called a shorthand property. The shorthand property for background is simply "background":
Examplebody {background:#ffffff url('img_tree.png') no-repeat right top;}When using the shorthand property the order of the property values is:
background-color background-image background-repeat background-attachment background-position
It does not matter if one of the property values is missing, as long as the ones that are present are in this order.
All CSS Background Properties
Property Description
background Sets all the background properties in one declaration
background-attachmentSets whether a background image is fixed or scrolls with the rest of the page
background-color Sets the background color of an element
background-image Sets the background image for an element
background-position Sets the starting position of a background image
background-repeat Sets how a background image will be repeated
CSS Text TEXT FORMATTING
Text Color
33
The color property is used to set the color of the text. With CSS, a color is most often specified by:
a HEX value - like "#ff0000"
an RGB value - like "rgb(255,0,0)" a color name - like "red"
The default color for a page is defined in the body selector.
Examplebody {color:blue;}h1 {color:#00ff00;}h2 {color:rgb(255,0,0);}
For W3C compliant CSS: If you define the color property, you must also define the background-color property.
Text AlignmentThe text-align property is used to set the horizontal alignment of a text. Text can be centered, or aligned to the left or right, or justified. When text-align is set to "justify", each line is stretched so that every line has equal width, and the left and right margins are straight (like in magazines and newspapers).
Exampleh1 {text-align:center;}p.date {text-align:right;}p.main {text-align:justify;}
Text DecorationThe text-decoration property is used to set or remove decorations from text. The text-decoration property is mostly used to remove underlines from links for design purposes:
34
Examplea {text-decoration:none;} It can also be used to decorate text:
Exampleh1 {text-decoration:overline;}h2 {text-decoration:line-through;}h3 {text-decoration:underline;}h4 {text-decoration:blink;}
It is not recommended to underline text that is not a link, as this often confuses users.
Text TransformationThe text-transform property is used to specify uppercase and lowercase letters in a text. It can be used to turn everything into uppercase or lowercase letters, or capitalize the first letter of each word.
Examplep.uppercase {text-transform:uppercase;}p.lowercase {text-transform:lowercase;}p.capitalize {text-transform:capitalize;}
Text IndentationThe text-indentation property is used to specify the indentation of the first line of a text.
Examplep {text-indent:50px;}
35
All CSS Text Properties
Property Description
color Sets the color of text
direction Specifies the text direction/writing direction
letter-spacingIncreases or decreases the space between characters in a text
line-height Sets the line height
text-align Specifies the horizontal alignment of text
text-decoration
Specifies the decoration added to text
text-indent Specifies the indentation of the first line in a text-block
text-shadow Specifies the shadow effect added to text
text-transform Controls the capitalization of text
unicode-bidi
vertical-align Sets the vertical alignment of an element
white-space Specifies how white-space inside an element is handled
word-spacing
Increases or decreases the space between words in a text
36
CSS FontCSS font properties define the font family, boldness, size, and the style of a text.
Difference Between Serif and Sans-serif Fonts
On computer screens, sans-serif fonts are considered easier to read than serif fonts.
CSS Font FamiliesIn CSS, there are two types of font family names:
generic family - a group of font families with a similar look (like "Serif" or "Monospace") font family - a specific font family (like "Times New Roman" or "Arial")
Generic family Font family Description
Serif
Times New RomanGeorgia
Serif fonts have small lines at the ends on some characters
Sans-serifArialVerdana
"Sans" means without - these fonts do not have the lines at the ends of characters
Monospace
Courier NewLucida Console
All monospace characters have the same width
Font FamilyThe font family of a text is set with the font-family property. The font-family property should hold several font names as a "fallback" system. If the browser does not support the first font, it tries the next font.
Start with the font you want, and end with a generic family, to let the browser pick a similar font in the generic family, if no other fonts are available. Note: If the name of a font family is more than one word, it must be in quotation marks, like font-family: "Times New Roman". More than one font family is specified in a comma-separated list:
37
Examplep{font-family:"Times New Roman", Times, serif;}
Font StyleThe font-style property is mostly used to specify italic text. This property has three values:
normal - The text is shown normally italic - The text is shown in italics oblique - The text is "leaning" (oblique is very similar to italic, but less supported)
Examplep.normal {font-style:normal;}p.italic {font-style:italic;}p.oblique {font-style:oblique;}
Font SizeThe font-size property sets the size of the text. Being able to manage the text size is important in web design. However, you should not use font size adjustments to make paragraphs look like headings, or headings look like paragraphs.
Always use the proper HTML tags, like <h1> - <h6> for headings and <p> for paragraphs. The font-size value can be an absolute, or relative size.
Absolute size:
Sets the text to a specified size Does not allow a user to change the text size in all browsers (bad for accessibility reasons) Absolute size is useful when the physical size of the output is known
Relative size:
Sets the size relative to surrounding elements Allows a user to change the text size in browsers
If you do not specify a font size, the default size for normal text, like paragraphs, is 16px (16px=1em).
Set Font Size With PixelsSetting the text size with pixels gives you full control over the text size:
38
Exampleh1 {font-size:40px;}h2 {font-size:30px;}p {font-size:14px;}
The example above allows Internet Explorer 9, Firefox, Chrome, Opera, and Safari to resize the text. Note: The example above does not work in IE, prior version 9. The text can be resized in all browsers using the zoom tool (however, this resizes the entire page, not just the text).
Set Font Size With EmTo avoid the resizing problem with older versions of Internet Explorer, many developers use em instead of pixels. The em size unit is recommended by the W3C.
1em is equal to the current font size. The default text size in browsers is 16px. So, the default size of 1em is 16px. The size can be calculated from pixels to em using this formula: pixels/16=em
Exampleh1 {font-size:2.5em;} /* 40px/16=2.5em */h2 {font-size:1.875em;} /* 30px/16=1.875em */p {font-size:0.875em;} /* 14px/16=0.875em */
In the example above, the text size in em is the same as the previous example in pixels. However, with the em size, it is possible to adjust the text size in all browsers.
Unfortunately, there is still a problem with older versions of IE. The text becomes larger than it should when made larger, and smaller than it should when made smaller.
Use a Combination of Percent and EmThe solution that works in all browsers, is to set a default font-size in percent for the <body> element:
Examplebody {font-size:100%;}h1 {font-size:2.5em;}h2 {font-size:1.875em;}p {font-size:0.875em;}
Our code now works great! It shows the same text size in all browsers, and allows all browsers to zoom or resize the text!
39
40
All CSS Font Properties
Property Description
font Sets all the font properties in one declaration
font-family Specifies the font family for text
font-size Specifies the font size of text
font-style Specifies the font style for text
font-variantSpecifies whether or not a text should be displayed in a small-caps font
font-weight Specifies the weight of a font
CSS Links
Styling LinksLinks can be styled with any CSS property (e.g. color, font-family, background, etc.).
Special for links are that they can be styled differently depending on what state they are in.
The four links states are:
a:link - a normal, unvisited link a:visited - a link the user has visited a:hover - a link when the user mouses over it a:active - a link the moment it is clicked
Examplea:link {color:#FF0000;} /* unvisited link */a:visited {color:#00FF00;} /* visited link */a:hover {color:#FF00FF;} /* mouse over link */a:active {color:#0000FF;} /* selected link */
When setting the style for several link states, there are some order rules:
a:hover MUST come after a:link and a:visited a:active MUST come after a:hover
41
Common Link Styles In the example above the link changes color depending on what state it is in. Lets go through some of the other common ways to style links:
Text DecorationThe text-decoration property is mostly used to remove underlines from links:
Examplea:link {text-decoration:none;}a:visited {text-decoration:none;}a:hover {text-decoration:underline;}a:active {text-decoration:underline;}
Background ColorThe background-color property specifies the background color for links:
Examplea:link {background-color:#B2FF99;}a:visited {background-color:#FFFF85;}a:hover {background-color:#FF704D;}a:active {background-color:#FF704D;}
CSS Lists The CSS list properties allow you to:
Set different list item markers for ordered lists Set different list item markers for unordered lists
Set an image as the list item markerList
In HTML, there are two types of lists:unordered lists - the list items are marked with bullets
ordered lists - the list items are marked with numbers or letters
Different List Item MarkersThe type of list item marker is specified with the list-style-type property:
Example
42
ul.a {list-style-type: circle;}ul.b {list-style-type: square;}
ol.c {list-style-type: upper-roman;}ol.d {list-style-type: lower-alpha;}Some of the values are for unordered lists, and some for ordered lists.
An Image as The List Item MarkerTo specify an image as the list item marker, use the list-style-image property:
Exampleul{list-style-image: url('sqpurple.gif');}The example above does not display equally in all browsers. IE and Opera will display the image-marker a little bit higher than Firefox, Chrome, and Safari.
If you want the image-marker to be placed equally in all browsers, a crossbrowser solution is explained below.
Crossbrowser Solution The following example displays the image-marker equally in all browsers:
Exampleul{list-style-type: none;padding: 0px;margin: 0px;}ul li{background-image: url(sqpurple.gif);background-repeat: no-repeat;background-position: 0px 5px; padding-left: 14px; }
Example
For ul: Set the list-style-type to none to remove the list item marker
Set both padding and margin to 0px (for cross-browser compatibility)
For all li in ul:
43
o Set the URL of the image, and show it only once (no-repeat)o Position the image where you want it (left 0px and down 5px)o Position the text in the list with padding-left
List - Shorthand propertyIt is also possible to specify all the list properties in one, single property. This is called a shorthand property.
The shorthand property used for lists, is the list-style property:
Exampleul{list-style: square url("sqpurple.gif");}When using the shorthand property, the order of the values are:
list-style-type list-style-position (for a description, see the CSS properties table below) list-style-image
It does not matter if one of the values above are missing, as long as the rest are in the specified order.
All CSS List Properties
Property Description
list-style Sets all the properties for a list in one declaration
list-style-image Specifies an image as the list-item marker
list-style-positionSpecifies if the list-item markers should appear inside or outside the content flow
list-style-type Specifies the type of list-item marker
CSS Tables The look of an HTML table can be greatly improved with CSS:
Company Contact Country
Alfreds Futterkiste Maria Anders Germany
Berglunds snabbköp Christina Berglund Sweden
Centro comercial Moctezuma Francisco Chang Mexico
44
Ernst Handel Roland Mendel Austria
Island Trading Helen Bennett UK
Königlich Essen Philip Cramer Germany
Laughing Bacchus Winecellars Yoshi Tannamuri Canada
Magazzini Alimentari Riuniti Giovanni Rovelli Italy
North/South Simon Crowther UK
Paris spécialités Marie Bertrand France
The Big Cheese Liz Nixon USA
Vaffeljernet Palle Ibsen Denmark
Table BordersTo specify table borders in CSS, use the border property.The example below specifies a black border for table, th, and td elements:
Exampletable, th, td{border: 1px solid black;}
Notice that the table in the example above has double borders. This is because both the table and the th/td elements have separate borders.To display a single border for the table, use the border-collapse property.
Collapse BordersThe border-collapse property sets whether the table borders are collapsed into a single border or separated:
Exampletable{border-collapse:collapse;}table,th, td{
45
border: 1px solid black;}
Table Width and HeightWidth and height of a table is defined by the width and height properties.The example below sets the width of the table to 100%, and the height of the th elements to 50px:
Exampletable {width:100%;}th{height:50px;}
Table Text AlignmentThe text in a table is aligned with the text-align and vertical-align properties.The text-align property sets the horizontal alignment, like left, right, or center:
Exampletd{text-align:right;}The vertical-align property sets the vertical alignment, like top, bottom, or middle:
Exampletd{height:50px;vertical-align:bottom;}
46
Table PaddingTo control the space between the border and content in a table, use the padding property on td and th elements:
Exampletd{padding:15px;}
Table ColorThe example below specifies the color of the borders, and the text and background color of th elements:
Exampletable, td, th{border:1px solid green;}th{background-color:green;color:white;
47
JAVASCRIPT INTRODUCTIONJavaScript is the world's most popular programming language. It is the language for HTML and the web, for servers, PCs, laptops, tablets, smart phones, and more.
JavaScript is a Scripting LanguageA scripting language is a lightweight programming language.
JavaScript is programming code that can be inserted into HTML pages.
JavaScript inserted into HTML pages, can be executed by all modern web browsers.
JavaScript is easy to learn.
What You Will LearnBelow is a taste of what you will learn in this tutorial.
JavaScript: Writing Into HTML Output
Exampledocument.write("<h1>This is a heading</h1>");document.write("<p>This is a paragraph</p>");
You can only use document.write in the HTML output. If you use it after the document has loaded, the whole document will be overwritten.
48
JavaScript: Reacting to Events
Example<button type="button" onclick="alert('Welcome!')">Click Me!</button>
The alert() function is not much used in JavaScript, but it is often quite handy for trying out code.
The onclick event is only one of the many HTML events you will learn about in this tutorial.
JavaScript: Changing HTML ContentUsing JavaScript to manipulate the content of HTML elements is a very powerful functionality.
Examplex=document.getElementById("demo") //Find the elementx.innerHTML="Hello JavaScript"; //Change the content
You will often see document.getElementByID("some id"). This is defined in the HTML DOM.
The DOM (Document Object Model) is the official W3C standard for accessing HTML elements.
JavaScript: Changing HTML StylesChanging the style of an HTML element, is a variant of changing an HTML attribute.
Examplex=document.getElementById("demo") //Find the element x.style.color="#ff0000"; //Change the style
49
JavaScript: Validate InputJavaScript is commonly used to validate input.
Exampleif isNaN(x) {alert("Not Numeric")};
Did You Know?JavaScript and Java are two completely different languages, in both concept and design.Java (invented by Sun) is a more complex programming language in the same category as C.
ECMA-262 is the official name of the JavaScript standard.
JavaScript was invented by Brendan Eich. It appeared in Netscape (a no longer existing browser) in 1995, and has been adopted by ECMA (a standard association) since 1997
Scripts in HTML must be inserted between <script> and </script> tags.
Scripts can be put in the <body> and in the <head> section of an HTML page.
The <script> TagTo insert a JavaScript into an HTML page, use the <script> tag.
The <script> and </script> tells where the JavaScript starts and ends.
The lines between the <script> and </script> contain the JavaScript:
<script>alert("My First JavaScript");</script>
You don't have to understand the code above. Just take it for a fact, that the browser will interpret and execute the JavaScript code between the <script> and </script> tags.
Old examples may have type="text/javascript" in the <script> tag. This is no longer required. JavaScript is the default scripting language in all modern browsers and in HTML5.
50
JavaScript in <body>In this example, JavaScript writes into the HTML <body> while the page loads:
Example<!DOCTYPE html><html><body>..<script>document.write("<h1>This is a heading</h1>");document.write("<p>This is a paragraph</p>");</script>..</body></html>
JavaScript Functions and EventsThe JavaScript statements in the example above, are executed while the page loads.
More often, we want to execute code when an event occurs, like when the user clicks a button.
If we put JavaScript code inside a function, we can call that function when an event occurs.
You will learn much more about JavaScript functions and events in later chapters.
JavaScript in <head> or <body>You can place an unlimited number of scripts in an HTML document.
Scripts can be in the <body> or in the <head> section of HTML, and/or in both.
It is a common practice to put functions in the <head> section, or at the bottom of the page. This way they are all in one place and do not interfere with page content.
51
A JavaScript Function in <head>In this example, a JavaScript function is placed in the <head> section of an HTML page.
The function is called when a button is clicked:
Example<!DOCTYPE html><html>
<head><script>function myFunction(){document.getElementById("demo").innerHTML="My First JavaScript Function";}</script></head>
<body>
<h1>My Web Page</h1>
<p id="demo">A Paragraph</p>
<button type="button" onclick="myFunction()">Try it</button>
</body></html>
A JavaScript Function in <body>In this example, a JavaScript function is placed in the <body> section of an HTML page.
The function is called when a button is clicked:
Example<!DOCTYPE html><html><body>
52
<h1>My Web Page</h1>
<p id="demo">A Paragraph</p>
<button type="button" onclick="myFunction()">Try it</button>
<script>function myFunction(){document.getElementById("demo").innerHTML="My First JavaScript Function";}</script>
</body></html>
External JavaScriptsScripts can also be placed in external files. External files often contain code to be used by several different web pages.
External JavaScript files have the file extension .js.
To use an external script, point to the .js file in the "src" attribute of the <script> tag:
Example<!DOCTYPE html><html><body><script src="myScript.js"></script></body></html>
You can place the script in the <head> or <body> as you like. The script will behave as if it was located exactly where you put the <script> tag in the document.
External scripts cannot contain <script> tags.
JavaScript Variables
53
JavaScript variables are "containers" for storing information:
Examplevar x=5;var y=6;var z=x+y;
Much Like Algebrax=5y=6z=x+y
In algebra we use letters (like x) to hold values (like 5).
From the expression z=x+y above, we can calculate the value of z to be 11.
In JavaScript these letters are called variables.
JavaScript VariablesAs with algebra, JavaScript variables can be used to hold values (x=5) or expressions (z=x+y).
Variable can have short names (like x and y) or more descriptive names (age, sum, totalvolume).
Variable names must begin with a letter Variable names can also begin with $ and _ (but we will not use it) Variable names are case sensitive (y and Y are different variables)
Both JavaScript statements and JavaScript variables are case-sensitive.
JavaScript Data TypesJavaScript variables can also hold other types of data, like text values (name="John Doe").
In JavaScript a text like "John Doe" is called a string.
54
There are many types of JavaScript variables, but for now, just think of numbers and strings.
When you assign a text value to a variable, put double or single quotes around the value.
When you assign a numeric value to a variable, do not put quotes around the value. If you put quotes around a numeric value, it will be treated as text.
Examplevar pi=3.14;var name="John Doe";var answer='Yes I am!';
Declaring (Creating) JavaScript VariablesCreating a variable in JavaScript is most often referred to as "declaring" a variable.
You declare JavaScript variables with the var keyword:
var carname;
After the declaration, the variable is empty (it has no value).
To assign a value to the variable, use the equal sign:
carname="Volvo";
However, you can also assign a value to the variable when you declare it:
var carname="Volvo";
In the example below we create a variable called carname, assigns the value "Volvo" to it, and put the value inside the HTML paragraph with id="demo":
Example<p id="demo"></p>var carname="Volvo";document.getElementById("demo").innerHTML=carname;
It's a good programming practice to declare all the variables you will need, in one place, at the beginning of your code.
55
One Statement, Many VariablesYou can declare many variables in one statement. Just start the statement with var and separate the variables by comma:
var name="Doe", age=30, job="carpenter";
Your declaration can also span multiple lines:
var name="Doe",age=30,job="carpenter";
Value = undefinedIn computer programs, variables are often declared without a value. The value can be something that has to be calculated, or something that will be provided later, like user input. Variable declared without a value will have the value undefined.
The variable carname will have the value undefined after the execution of the following statement:
var carname;
Re-Declaring JavaScript VariablesIf you re-declare a JavaScript variable, it will not lose its value:.
The value of the variable carname will still have the value "Volvo" after the execution of the following two statements:
var carname="Volvo"; var carname;
JavaScript Arithmetic
56
As with algebra, you can do arithmetic with JavaScript variables, using operators like = and +:
Exampley=5;x=y+2;
JavaScript Statements
JavaScript is a sequence of statements to be executed by the browser.
JavaScript StatementsJavaScript statements are "commands" to the browser. The purpose of the statements is to tell the browser what to do.
This JavaScript statement tells the browser to write "Hello Dolly" inside an HTML element with id="demo":
document.getElementById("demo").innerHTML="Hello Dolly";
Semicolon ;Semicolon separates JavaScript statements.
Normally you add a semicolon at the end of each executable statement.
Using semicolons also makes it possible to write many statements on one line.
You might see examples without semicolons. Ending statements with semicolon is optional in JavaScript.
JavaScript CodeJavaScript code (or just JavaScript) is a sequence of JavaScript statements.
57
Each statement is executed by the browser in the sequence they are written.
This example will manipulate two HTML elements:
Exampledocument.getElementById("demo").innerHTML="Hello Dolly";document.getElementById("myDIV").innerHTML="How are you?";
JavaScript Code BlocksJavaScript statements can be grouped together in blocks.
Blocks start with a left curly bracket, and end with a right curly bracket.
The purpose of a block is to make the sequence of statements execute together.
A good example of statements grouped together in blocks, are JavaScript functions.
This example will run a function that will manipulate two HTML elements:
Examplefunction myFunction(){document.getElementById("demo").innerHTML="Hello Dolly";document.getElementById("myDIV").innerHTML="How are you?";}
JavaScript is Case SensitiveJavaScript is case sensitive.
Watch your capitalization closely when you write JavaScript statements:
A function getElementById is not the same as getElementbyID.
A variable named myVariable is not the same as MyVariable.
White SpaceJavaScript ignores extra spaces. You can add white space to your script to make it more readable. The following lines are equivalent:
58
var name="Hege";var name = "Hege";
Break up a Code LineYou can break up a code line within a text string with a backslash. The example below will be displayed properly:
document.write("Hello \World!");
However, you cannot break up a code line like this:
document.write \("Hello World!");
Did You Know?JavaScript is a scripting language. Scripting code is executed line by line while the browser reads it. With traditional programming, all the code has to be compiled before it can be
JavaScript If...Else Statements
Conditional statements are used to perform different actions based on different conditions.
Conditional StatementsVery often when you write code, you want to perform different actions for different decisions. You can use conditional statements in your code to do this.
In JavaScript we have the following conditional statements:
if statement - use this statement to execute some code only if a specified condition is true
if...else statement - use this statement to execute some code if the condition is true and another code if the condition is false
59
if...else if....else statement - use this statement to select one of many blocks of code to be executed
switch statement - use this statement to select one of many blocks of code to be executed
If StatementUse the if statement to execute some code only if a specified condition is true.
Syntaxif (condition) { code to be executed if condition is true }
Note that if is written in lowercase letters. Using uppercase letters (IF) will generate a JavaScript error!
ExampleMake a "Good day" greeting if the time if less than 20:00:
if (time<20) { x="Good day"; }
The result of x will be:
Good day
Notice that there is no ..else.. in this syntax. You tell the browser to execute some code only if the specified condition is true.
If...else StatementUse the if....else statement to execute some code if a condition is true and another code if the condition is not true.
Syntaxif (condition) { code to be executed if condition is true }
60
else { code to be executed if condition is not true }
ExampleIf the time is less than 20:00, you will get a "Good day" greeting, otherwise you will get a "Good evening" greeting
if (time<20) { x="Good day"; }else { x="Good evening"; }
The result of x will be:
Good day
If...else if...else StatementUse the if....else if...else statement to select one of several blocks of code to be executed.
Syntaxif (condition1) { code to be executed if condition1 is true }else if (condition2) { code to be executed if condition2 is true }else { code to be executed if neither condition1 nor condition2 is true }
Example
61
If the time is less than 10:00, you will get a "Good morning" greeting, if not, but the time is less than 20:00, you will get a "Good day" greeting, otherwise you will get a "Good evening" greeting:
if (time<10) { x="Good morning"; }else if (time<20) { x="Good day"; }else { x="Good evening"; }
The result of x will be:
Good day
JavaScript Popup Boxes
JavaScript has three kind of popup boxes: Alert box, Confirm box, and Prompt box.
Alert BoxAn alert box is often used if you want to make sure information comes through to the user.
When an alert box pops up, the user will have to click "OK" to proceed.
Syntaxwindow.alert("sometext");
The window.alert method can be written without the window prefix.
Example<!DOCTYPE html><html><head><script>function myFunction(){
62
alert("I am an alert box!");}</script></head><body>
<input type="button" onclick="myFunction()" value="Show alert box">
</body></html>
Confirm BoxA confirm box is often used if you want the user to verify or accept something.
When a confirm box pops up, the user will have to click either "OK" or "Cancel" to proceed.
If the user clicks "OK", the box returns true. If the user clicks "Cancel", the box returns false.
Syntaxwindow.confirm("sometext");
The window.confirm() method can be written without the window prefix.
Examplevar r=confirm("Press a button");if (r==true) { x="You pressed OK!"; }else { x="You pressed Cancel!"; }
Prompt BoxA prompt box is often used if you want the user to input a value before entering a page.
When a prompt box pops up, the user will have to click either "OK" or "Cancel" to proceed after entering an input value.
If the user clicks "OK" the box returns the input value. If the user clicks "Cancel" the
63
box returns null.
Syntaxwindow.prompt("sometext","defaultvalue");
The window.prompt() method can be written without the window prefix.
Examplevar name=prompt("Please enter your name","Harry Potter");if (name!=null && name!="") { x="Hello " + name + "! How are you today?"; }
Line BreaksTo display line breaks inside a popup box, use a back-slash followed by the character n.
Examplealert("Hello\nHow are you?");
JavaScript Functions
A function is a block of code that will be executed when "someone" calls it:
Example<!DOCTYPE html><html><head><script>function myFunction(){alert("Hello World!");}</script></head>
<body><button onclick="myFunction()">Try it</button>
64
</body></html>
JavaScript Function SyntaxA function is written as a code block (inside curly { } braces), preceded by the function keyword:
function functionname(){some code to be executed}
The code inside the function will be executed when "someone" calls the function.
The function can be called directly when an event occurs (like when a user clicks a button), and it can be called from "anywhere" by JavaScript code.
JavaScript is case sensitive. The function keyword must be written in lowercase letters, and the function must be called with the same capitals as used in the function name.
Calling a Function with ArgumentsWhen you call a function, you can pass along some values to it, these values are called arguments or parameters.
These arguments can be used inside the function.
You can send as many arguments as you like, separated by commas (,)
myFunction(argument1,argument2)
Declare the argument, as variables, when you declare the function:
function myFunction(var1,var2){some code}
The variables and the arguments must be in the expected order. The first variable is given the value of the first passed argument etc.
65
Example<button onclick="myFunction('Harry Potter','Wizard')">Try it</button>
<script>function myFunction(name,job){alert("Welcome " + name + ", the " + job);}</script>
The function above will alert "Welcome Harry Potter, the Wizard" when the button is clicked.
The function is flexible, you can call the function using different arguments, and different welcome messages will be given:
Example<button onclick="myFunction('Harry Potter','Wizard')">Try it</button><button onclick="myFunction('Bob','Builder')">Try it</button>
The example above will alert "Welcome Harry Potter, the Wizard" or "Welcome Bob, the Builder" depending on which button is clicked.
Functions With a Return ValueSometimes you want your function to return a value back to where the call was made.
This is possible by using the return statement.
When using the return statement, the function will stop executing, and return the specified value.
Syntaxfunction myFunction(){var x=5;return x;}
The function above will return the value 5.
66
Note: It is not the entire JavaScript that will stop executing, only the function. JavaScript will continue executing code, where the function-call was made from.
The function-call will be replaced with the returnvalue:
var myVar=myFunction();
The variable myVar holds the value 5, which is what the function "myFunction()" returns.
You can also use the returnvalue without storing it as a variable:
document.getElementById("demo").innerHTML=myFunction();
The innerHTML of the "demo" element will be 5, which is what the function "myFunction()" returns.
You can make a returnvalue based on arguments passed into the function:
ExampleCalculate the product of two numbers, and return the result:
function myFunction(a,b){return a*b;}
document.getElementById("demo").innerHTML=myFunction(4,3);
The innerHTML of the "demo" element will be:
12
The return statement is also used when you simply want to exit a function. The return value is optional:
function myFunction(a,b){if (a>b) { return; }x=a+b}
The function above will exit the function if a>b, and will not calculate the sum of a and b.
67
Local JavaScript VariablesA variable declared (using var) within a JavaScript function becomes LOCAL and can only be accessed from within that function. (the variable has local scope).
You can have local variables with the same name in different functions, because local variables are only recognized by the function in which they are declared.
Local variables are deleted as soon as the function is completed.
Global JavaScript VariablesVariables declared outside a function, become GLOBAL, and all scripts and functions on the web page can access it.
The Lifetime of JavaScript VariablesThe lifetime JavaScript variables starts when they are declared.
Local variables are deleted when the function is completed.
Global variables are deleted when you close the page.
Assigning Values to Undeclared JavaScript VariablesIf you assign a value to variable that has not yet been declared, the variable will automatically be declared as a GLOBAL variable.
This statement:
carname="Volvo";
will declare the variable carname as a global variable , even if it is executed inside a function.
JavaScript HTML DOM Events
HTML DOM allows JavaScript to react to HTML events.
68
Example
Mouse Over Me
Click Me
Reacting to EventsA JavaScript can be executed when an event occurs, like when a user clicks on an HTML element.
To execute code when a user clicks on an element, add JavaScript code to an HTML event attribute:
onclick=JavaScript
Examples of HTML events:
When a user clicks the mouse When a web page has loaded When an image has been loaded When the mouse moves over an element When an input field is changed When an HTML form is submitted When a user strokes a key
In this example, the content of the <h1> element is changed when a user clicks on it:
Example<!DOCTYPE html><html><body><h1 onclick="this.innerHTML='Ooops!'">Click on this text!</h1></body></html>
In this example, a function is called from the event handler:
Example<!DOCTYPE html><html>
69
<head><script>function changetext(id){id.innerHTML="Ooops!";}</script></head><body><h1 onclick="changetext(this)">Click on this text!</h1></body></html>
HTML Event AttributesTo assign events to HTML elements you can use event attributes.
ExampleAssign an onclick event to a button element:
<button onclick="displayDate()">Try it</button>
In the example above, a function named displayDate will be executed when the button is clicked.
Assign Events Using the HTML DOMThe HTML DOM allows you to assign events to HTML elements using JavaScript:
ExampleAssign an onclick event to a button element:
<script>document.getElementById("myBtn").onclick=function(){displayDate()};</script>
In the example above, a function named displayDate is assigned to an HTML element with the id=myButn".
The function will be executed when the button is clicked.
The onload and onunload Events
70
The onload and onunload events are triggered when the user enters or leaves the page.
The onload event can be used to check the visitor's browser type and browser version, and load the proper version of the web page based on the information.
The onload and onunload events can be used to deal with cookies.
Example<body onload="checkCookies()">
The onchange EventThe onchange event are often used in combination with validation of input fields.
Below is an example of how to use the onchange. The upperCase() function will be called when a user changes the content of an input field.
Example<input type="text" id="fname" onchange="upperCase()">
The onmouseover and onmouseout EventsThe onmouseover and onmouseout events can be used to trigger a function when the user mouses over, or out of, an HTML element.
ExampleA simple onmouseover-onmouseout example:
Mouse Over Me
The onmousedown, onmouseup and onclick EventsThe onmousedown, onmouseup, and onclick events are all parts of a mouse-click. First when a mouse-button is clicked, the onmousedown event is triggered, then, when the mouse-button is released, the onmouseup event is triggered, finally, when the mouse-
71
click is completed, the onclick event is triggered.
ExampleA simple onmousedown-onmouseup example:
Click Me
JavaScript Array Object
The Array object is used to store multiple values in a single variable.
Try it Yourself - ExamplesCreate an array, and assign values to it:
Examplevar mycars = new Array();mycars[0] = "Saab";mycars[1] = "Volvo";mycars[2] = "BMW";
What is an Array?An array is a special variable, which can hold more than one value at a time.
If you have a list of items (a list of car names, for example), storing the cars in single variables could look like this:
var car1="Saab";var car2="Volvo";var car3="BMW";
However, what if you want to loop through the cars and find a specific one? And what if you had not 3 cars, but 300?
72
The solution is an array!
An array can hold many values under a single name, and you can access the values by referring to an index number.
Create an ArrayAn array can be created in three ways.
The following code creates an Array object called myCars:
1: Regular:
var myCars=new Array(); myCars[0]="Saab"; myCars[1]="Volvo";myCars[2]="BMW";
2: Condensed:
var myCars=new Array("Saab","Volvo","BMW");
3: Literal:
var myCars=["Saab","Volvo","BMW"];
Access an ArrayYou refer to an element in an array by referring to the index number.
This statement access the value of the first element in myCars:
var name=myCars[0];
This statement modifies the first element in myCars:
myCars[0]="Opel";
[0] is the first element in an array. [1] is the second . . . . . (indexes start with 0)
73
You Can Have Different Objects in One ArrayAll JavaScript variables are objects. Array elements are objects. Functions are objects.
Because of this, you can have variables of different types in the same Array.
You can have objects in an Array. You can have functions in an Array. You can have arrays in an Array:
myArray[0]=Date.now;myArray[1]=myFunction;myArray[2]=myCars;
Array Methods and PropertiesThe Array object has predefined properties and methods:
var x=myCars.length // the number of elements in myCarsvar y=myCars.indexOf("Volvo") // the index position of "Volvo"
Create New MethodsPrototype is a global constructor in JavaScript. It can construct new properties and methods for any JavaScript Objects.
Example: Make a new Array method.Array.prototype.ucase=function(){ for (i=0;i<this.length;i++) {this[i]=this[i].toUpperCase();}}
JavaScript String Object
74
The String object is used for storing and manipulating text.
JavaScript StringsA string simply stores a series of characters like "John Doe".
A string can be any text inside quotes. You can use simple or double quotes:
Examplevar carname="Volvo XC60";var carname='Volvo XC60';
You can access each character in a string with its position (index):
Examplevar character=carname[7];
String indexes are zero-based, which means the first character is [0], the second is [1], and so on.
You can use quotes inside a string, as long as they don't match the quotes surrounding the string:
Examplevar answer="It's alright";var answer="He is called 'Johnny'";var answer='He is called "Johnny"';
Or you can put quotes inside a string by using the \ escape character:
Examplevar answer='It\'s alright';var answer="He is called \"Johnny\"";
String LengthThe length of a string (a string object) is found in the built in property length:
Example
75
var txt="Hello World!";document.write(txt.length);
var txt="ABCDEFGHIJKLMNOPQRSTUVWXYZ";document.write(txt.length);
Finding a String in a StringThe indexOf() method returns the position (as a number) of the first found occurrence of a specified text inside a string:
Examplevar str="Hello world, welcome to the universe.";var n=str.indexOf("welcome");
The method returns -1 if the specified text is not found.
The lastIndexOf() method starts searching at the end of the string instead of at the beginning.
Matching ContentThe match() method can be used to search for a matching content in a string:
Examplevar str="Hello world!";document.write(str.match("world") + "<br>");document.write(str.match("World") + "<br>");document.write(str.match("world!"));
Replacing ContentThe replace() method replaces a specified value with another value in a string.
Examplestr="Please visit Microsoft!"var n=str.replace("Microsoft","W3Schools");
76
Upper Case and Lower CaseA string is converted to upper/lower case with the methods toUpperCase() / toLowerCase():
Examplevar txt="Hello World!"; // Stringvar txt1=txt.toUpperCase(); // txt1 is txt converted to uppervar txt2=txt.toLowerCase(); // txt2 is txt converted to lower
Convert a String to an ArrayA string is converted to an array with the built in method string.split():
Exampletxt="a,b,c,d,e" // Stringtxt.split(","); // Split on commastxt.split(" "); // Split on spacestxt.split("|"); // Split on pipe
Special CharactersThe backslash (\) can be used to insert apostrophes, new lines, quotes, and other special characters into a string.
Look at the following JavaScript code:
var txt="We are the so-called "Vikings" from the north.";document.write(txt);
In JavaScript, a string is started and stopped with either single or double quotes. This means that the string above will be chopped to: We are the so-called
To solve this problem, you must place a backslash (\) before each double quote in "Viking". This turns each double quote into a string literal:
var txt="We are the so-called \"Vikings\" from the north.";document.write(txt);
JavaScript will now output the proper text string: We are the so-called "Vikings" from the north.
The table below lists other special characters that can be added to a text string with the backslash sign:
77
Code Outputs
\' single quote
\" double quote
\\ backslash
\n new line
\r carriage return
\t tab
\b backspace
\f form feed
String Properties and MethodsProperties:
length prototype constructor
Methods:
charAt() charCodeAt() concat() fromCharCode() indexOf() lastIndexOf() match() replace() search() slice() split() substr() substring() toLowerCase() toUpperCase() valueOf()
JavaScript Date Object
78
The Date object is used to work with dates and times.
Return today's date and timeHow to use the Date() method to get today's date.
getFullYear()Use getFullYear() to get the year.
getTime()getTime() returns the number of milliseconds since 01.01.1970.
setFullYear()How to use setFullYear() to set a specific date.
toUTCString()How to use toUTCString() to convert today's date (according to UTC) to a string.
getDay()Use getDay() and an array to write a weekday, and not just a number.
Display a clockHow to display a clock on your web page.
Create a Date ObjectThe Date object is used to work with dates and times.
Date objects are created with the Date() constructor.
There are four ways of initiating a date:
new Date() // current date and timenew Date(milliseconds) //milliseconds since 1970/01/01new Date(dateString)new Date(year, month, day, hours, minutes, seconds, milliseconds)
Most parameters above are optional. Not specifying, causes 0 to be passed in.
Once a Date object is created, a number of methods allow you to operate on it. Most methods allow you to get and set the year, month, day, hour, minute, second, and milliseconds of the object, using either local time or UTC (universal, or GMT) time.
All dates are calculated in milliseconds from 01 January, 1970 00:00:00 Universal Time (UTC) with a day containing 86,400,000 milliseconds.
Some examples of initiating a date:
var today = new Date()
79
var d1 = new Date("October 13, 1975 11:13:00")var d2 = new Date(79,5,24)var d3 = new Date(79,5,24,11,33,0)
Set DatesWe can easily manipulate the date by using the methods available for the Date object.
In the example below we set a Date object to a specific date (14th January 2010):
var myDate=new Date();myDate.setFullYear(2010,0,14);
And in the following example we set a Date object to be 5 days into the future:
var myDate=new Date();myDate.setDate(myDate.getDate()+5);
Note: If adding five days to a date shifts the month or year, the changes are handled automatically by the Date object itself!
Compare Two DatesThe Date object is also used to compare two dates.
The following example compares today's date with the 14th January 2100:
var x=new Date();x.setFullYear(2100,0,14);var today = new Date();
if (x>today) { alert("Today is before 14th January 2100"); }else { alert("Today is after 14th January 2100"); }
80
What is RegExp?RegExp, is short for regular expression.
A regular expression is an object that describes a pattern of characters.
When you search in a text, you can use a pattern to describe what you are searching for.
A simple pattern can be one single character.
A more complicated pattern can consist of more characters, and can be used for parsing, format checking, substitution and more.
Regular expressions are used to perform powerful pattern-matching and "search-and-replace" functions on text.
Syntaxvar patt=new RegExp(pattern,modifiers);
or more simply:
var patt=/pattern/modifiers;
pattern specifies the pattern of an expression modifiers specify if a search should be global, case-sensitive, etc.
RegExp ModifiersModifiers are used to perform case-insensitive and global searches.
The i modifier is used to perform case-insensitive matching.
The g modifier is used to perform a global match (find all matches rather than stopping after the first match).
Example 1Do a case-insensitive search for "w3schools" in a string:
var str="Visit Restarttechnologies ";var patt1=/ Restarttechnologies /i;
The marked text below shows where the expression gets a match:
81
Visit Restarttechnologies
Example 2Do a global search for "is":
var str="Is this all there is?";var patt1=/is/g;
The marked text below shows where the expression gets a match:
Is this all there is?
Example 3Do a global, case-insensitive search for "is":
var str="Is this all there is?";var patt1=/is/gi;
The marked text below shows where the expression gets a match:
Is this all there is?
test()The test() method searches a string for a specified value, and returns true or false, depending on the result.
The following example searches a string for the character "e":
Examplevar patt1=new RegExp("e");document.write(patt1.test("The best things in life are free"));
Since there is an "e" in the string, the output of the code above will be:
true
82
exec()The exec() method searches a string for a specified value, and returns the text of the found value. If no match is found, it returns null.
The following example searches a string for the character "e":
Example 1var patt1=new RegExp("e");document.write(patt1.exec("The best things in life are free"));
Since there is an "e" in the string, the output of the code above will be:
e