html javascript and css

HTML/JavaScript/CSS

History

What is the relationship between: SGML HTML XHTML CSS JavaScript

History

MarkupAnnotations instructing how the document

should appear in printWord processors use different markup

schemesSGML

IBM - Standard Generalized Markup LanguageMarkup instructions stored with ASCII file

Any computer could render document Lilly Example

History

HTMLTim Berners-Lee created HTML – subset of

SGMLNot platform or application specificOnly server software needed to publish file s

on the net Structure versus content

Browser parses HTML file into a tree

History

Sample HTML File<FONT SIZE=14 FACE=Swing><B>Bryan Moore</B><BR></FONT><FONT SIZE=12 FACE=Textile>1234 Sunset Ave. <BR>Walla Walla, WA 12345 <BR>(123)123.4567<BR></FONT>

Web Applications and Real World Design - Knuckles

History


Browser parse tree

History

Problems with extracting dataNeed to write a computer program to extract

the names and addresses by selecting text strings following font tags

Content and structure of document become intertwined

Not the intention of SGML and original HTML Cascading Style Sheets

Attempt to separate content and style

History

CSSCan alter the look of entire file with a simple

coding changeCan keep styles in an external file Increases the knowledge needed to code

pagesInitial rationale of HTML was to appeal to the

masses

History

Parse tree using CSS


Still need to reference

Information based on

“second string after BR”

Information is not

meaningful

History

Extensible Markup Language XMLExtensible- can create own tagsComplete separation of content and style


History

Releases HTML 4.0 1997 XML 1.0 1998

XML and HTML need to better cooperate XHTML 1.0 2000

XHTML Contains elements and attributes of HTML Elements must have closing tags Lowercase Attributes must have values Attributes in single or double quotes

http://www.w3schools.com/xhtml/default.asp

HTML Forms and JavaScript

Client Server Model Client Side Processing

JavaScript downloaded from web page and processed by the client – typically form checking

JavaScript can interact directly with form data Server Side processing

Information from a form sent to server for processing PHP Perl C++ Server can interact directly with the form data

HTML Forms and JavaScript

JavaScriptHTML files are text filesJavaScript is interpreted not compiledObject oriented

HTML forms are objects and can be manipulated via JavaScript

Dynamic HTML – merger of JavaScript and HTML

Different implementations of DHTML by software companies

What is JavaScript

Scripting language (object-oriented) Lightweight programming language developed by Netscape Interpreted, not compiled

Designed to be embedded in browsers Ideal for adding interactivity to HTML pages Detect browser versions Work with info from user via HTML forms Create cookies Validate form data Read and write HTML elements

Supported by all major browsers Internet Explorer has JScript (started in IE3)

http://www.faqts.com/knowledge_base/view.phtml/aid/1380

It’s free, no license required

What is JavaScript

Syntax is similar to Java, but it’s not Java per se

Usually JavaScript code is embedded within HTML code using the script tag:

Can have more than one pair of script tags in a page

Semicolons: C++ and JAVA require them but in JavaScript it’s optional

What is JavaScript

HelloWorld example program…

<html> <head><title>JavaScript

HelloWorld!</title></head> <body> <script language="JavaScript"> document.write('Javascript says "Hello

World!"') </script> </body>

</html>

Let’s open it in the browser

What is JavaScript

Javascript can be located in the head, body or external fileHead section

Ensures script is loaded before trigger eventBody section

Script executes when body loadsExternal

Allows scripts to run on several pagesExamples:

http://www.w3schools.com/js/js_whereto.asp

What is JavaScript

JavaScript statements in head write to the beginning of the body section but don’t violate HTML code already there.

JavaScript statements in body write based on their location

JavaScript interpreted first then HTML interpreted secondDocument.write writes to the HTML document

not the web page

What is JavaScript <html> <head> <script language=“JavaScript”> document.write (“<b> This is first </b>); </script> </head>

<body> Now where does this print on the web page???? <br />

<script language=“JavaScript”> document.write ( “This might be last?”) </script>

</body> </html> Lets See what the answer is!

What is JavaScript

Now, let JavaScript generate HTML for us…

<html> <head><title>JavaScript HelloWorld!</title></head> <body> <script laguage="JavaScript"> document.write("<h2>Javascript-Generated output:</h2>

<p>This paragraph generated by JavaScript</p> <p>It can even insert an image</p> <img src='../assigns/RayWeb/images/cathedral.jpg' />")

</script> </body> </html>

Let’s open it in the browser

Identifier Etiquette

Identifier– The name of a variable (or function) Starts with a letter, can contains digits & underscores Case Sensitive!! Should be meaningful to someone reading your code

Good: accountBalance, amountDue

Bad: bal, due,

Just plain wrong: 2bOrNotToBe, +var, total-value

Variables

Must declare variables before they’re used in the program Declare at the top of the program & terminate each

statement with ‘;’ Intialize variables when appropriate Local variables (declared within a function) destroyed

after function exit. Can only be accessed within the function

Example – Note Assignments var candyBarPrice = 2.50; var taxRate = .075; var candyBarsPurchased;

Assignment Operator

Assignment ‘looks like’ equal sign but does NOT behave like it

subTotal = subTotal + 1.50

subTotal ‘is assigned the value’ that is currently in subTotal plus the value of 1.50

Expressions

An expression is a statement that describes a computation

Usually look like algebra formulas total = subTotal * taxRate

Operators (+, -, *, /, etc.) have different levels of precedence, similar to algebraDon’t rely on it! For clarity, use parentheses

w3Schools operator reference page

Conditional Statements--if

if (some boolean expression is true){

execute the statements within

the curly braces, otherwise skip to the first statement after the closing brace

}

Resume execution here in either case

Conditional Statements– if/else

if (some boolean expression is true){

execute these statements, otherwise skip to ‘else’ clause

}

else {

execute these statements if boolean expression is false

}

Resume execution here in either case

Conditional Test Program

Diagnostic messages indicate flow of control1. var variable1 = 1; var variable2 = 2;2. 3. if(variable1 >= 0){ 4. document.write(“<p> 1 is greater than 0

</p>"); 5. }6. document.write(“<p>Resuming execution after

'if' 7. statement</p>"); 8.

1. if(variable1 > variable2){ 2. document.write(“<p>1 is greater than

2</p>"); 3. } 4. else { 5. document.write(“<p>2 is greater than

1</p>"); 6. } • document.write("Resuming execution after

'if/else‘1. statement</p>");

Strings

Strings are sequences of keyboard characters enclosed in quotes “Hello World” or ‘Hello World’

Variables can hold strings var greeting = “Hello World”

String can be empty, i.e., contain no characters var myAnswer = “”

Use ‘\’ (escape symbol) to ‘type’ prohibited characters \b for backspace, \n for newline, \t for tab, \” for double

quote

JavaScript Functions – Basic Principles

AbstractionExperience has taught us that much code is

duplicated throughout program

Functions let us write the functionality once, then reuse it


Encapsulation Functions encapsulate a specific capability or feature

Function name allows us to access a function in our program

Parameterization We can customize the function’s result by passing in

different values each time we use it

Must use functions to write serious software!


Reasons to use functions Ease of communication Problem simplification Easier construction Code readability Reusability Maintainability

In JS, functions are the primary encapsulation mechanism

JavaScript Functions – Syntax

JS function syntax

function myFunctionName (list of parameters) {

….JS code here…

}

JavaScript Functions -- Issues

Key issues about using functions Naming functions Passing in parameters Using local variables within functions How to call (i.e., invoke) functions How to handle a function’s return value Where to put JS functions in your webpage

JavaScript Functions – Naming

Function names Name describes what function does Name is an identifier, so follow JS identifier syntax

rules & course coding standards

Example,findMaxValue(‘put some parameters here’)

JavaScript Functions -- Parameters

Passing parameters to the function Parameters provide functions with input Implicitly declared variables that can be accessed by

code within function body You provide actual input values when you call the

function Parameters are named variables separated by

commas

Example,function findMaxValue(num1, num2, num3)

JavaScript Functions – Where to put?

Put functions within <script>….</script> tags within the <head> section of the web page

<head>

<script language=“JavaScript”>

declare functions here….

</script>

</head>

JavaScript Functions – Local Variables

If needed, you can declare local variables within a function

local variable is visible only within the function body after it’s declared

Commonly used to store results of an intermediate calculation

JavaScript Functions – Local Variables

function findMaxValue(num1, num2,num3) { var tempMax; //local var

if (num1 >= num2) { tempMax = num1; }

else { tempMax = num2; }

if(num3 >= tempMax) { tempMax = num3; }

return tempMax;

} //end function

JavaScript Functions -- Calling

To call a function from your program, add a statement that contains the function name with values for the parameters the function requires

Example…somewhere in the <body>…., var x = 1, y = 4, z = 2;

findMaxValue(x, y, z);

What value does the function return? What happens with the result?

JavaScript Functions -- Return

Return keyword tells function to return some value and exit immediately

Function can have multiple return statements but only 1 can be executed in any given function call

Normally used to return the final result of a calculation to the calling program

For an example, see findMaxValue function

JavaScript Functions -- Return

Good Example Uses var maxNumber in calling program Function’s return value is assigned to maxNumber Display of maxNumber has correct value for inputs

Code snippet var x = 1, y = 4, z = 2;

var maxNumber = findMaxNumber(x, y, z);

document.write(“The maximum is: “ + maxNumber);

JavaScript Functions – Parameter Sequence

When calling functions, must enter parameters in same order as specified in function argument list.

1. function calculateDensity(height, width, depth, mass){2. var volume = height * width * depth;3. var density = mass / volume;4. return density;5. }6. ……………………………………………….7. var hth = 2, wth = 3, dth = 4, mass = 10;

1. var result = calculateDensity(2, 10, 3, 4);2. //returns .07 but correct answer is .42!!!

JavaScript Functions – Global Variables

Global variables are those declared outside of functions

Global variables are ‘visible’ from anywhere in the program, including inside functions

var globalHello = “Hello!”;

function writeHello() { document.write(globalHello); } // outputs “Hello!”

Example program

JavaScript Functions – Testing

Test each function thoroughly before proceeding with next programming task

Using multiple sets of inputs, be sure to test all possible outcomes

For each test, be sure calling program is properly handling return values

JavaScript Functions – Debugging

Use diagnostic output statements to trace program execution

Good places for diagnostic outputs Just before entering function Immediately upon entering function Before/In/After complex logic or computation Just before function return statement Immediately after function returns to calling program

JavaScript Functions

Built-In Functions PromptAlertConfirm

http://www.w3schools.com/js/js_popup.asp

JavaScript and HTML Forms

JavaScript ObjectsVar truck = new Object();Expression on right is a constructorProperties

truck.color=“white”document.write(color);

Primitives In JavaScript variable primitive types are

number, string and Boolean


Object Model for the Browser WindowCompound object structure is created when a

web page loads into a browserHierarchy

Window is an object, the HTML document is an object and its elements are objects

These objects have primitives associated with them


window [closed, location]

history [length]

document [bgColor, fgColor, URL, lastmodified,linkColor, vlinkColor]

images [properties] links [properties] frames [properties] forms [properties]


Window object is parent of structure window.closed is primitive that is Boolean window.location primitive contains string of the URL of

the HTML file window.document object is primary focus

When web page is loaded the HTML elements assign values to most of these window.document primitives

Often the word window is excluded as in document.write but need it if referring to multiple open windows

Properties can also be objects

JavaScript and HTML Forms <HTML> <HEAD> <TITLE>Document Properties</TITLE> <SCRIPT LANGUAGE=JavaScript></SCRIPT> </HEAD> <BODY TEXT="#0000FF" BGCOLOR="#FFFFCC"> <P>Blue text on a yellow background.<BR> <SCRIPT LANGUAGE=JavaScript></SCRIPT> </BODY> </HTML>

Interactive Programming on the Internet Knuckles


false#ffffff#00000001/10/2001 17:18:30 Blue text on a yellow background.

#ffffcc#0000ff

Interactive Programming on the Internet, Knuckles


MethodsBehavior associated with an objectEssentially functions that perform an actionSome are built in and others user made

Built-In Methods of the window objectConfirmAlertPrompt


User EventsAn event occurs when a user makes a change

to a form elementEx. Click a button, mouseover an image

Detection of an event done by event handlersEvent handler is an attribute of the HTML

button<form>

<input type=button value=“please click” onclick=“function name()”>

</form>

JavaScript and HTML Forms <HTML> <HEAD> <SCRIPT LANGUAGE=JavaScript></SCRIPT> </HEAD> <BODY> <P><FORM > <P><INPUT TYPE=button VALUE="Click Me"

onclick="changecolor()"> </FORM> </BODY> </HTML>

Interactive Programming on the Internet ,Knuckles


Form ObjectWindow.document.formA form is a property of the document but is

also an objectForm elements are properties of a form and

are also objectsAccess to form’s properties is done through

the NAME attribute of the FORM tagAccess to the properties of the form elements

is done through the NAME attributes of the particular form element


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JavaScript and HTML Forms <HTML> <HEAD> <SCRIPT LANGUAGE=JavaScript></SCRIPT> </HEAD> <BODY BGCOLOR="#FFFFCC"> <P><FORM name=addmult> <P>Enter a number in each field: <INPUT TYPE=text NAME=num1 VALUE="" SIZE=5> <INPUT TYPE=text NAME=num2 VALUE=""

SIZE=5><BR> <INPUT TYPE=button VALUE="+" onclick="plus()"> <INPUT TYPE=button VALUE="*"

onclick="times()"><BR> <INPUT TYPE=reset VALUE="Reset Form"><BR> <TEXTAREA NAME=result ROWS=3 COLS=27

WRAP=virtual></TEXTAREA> </FORM> </BODY> </HTML>

Interactive Programming on the Internet ,Knuckles

JavaScript and HTML FormsForm for submitting info for server side processing

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JavaScript and HTML Forms <HTML> <HEAD> <SCRIPT LANGUAGE=JavaScript></SCRIPT> </HEAD> <BODY BGCOLOR="#FFFFCC"> <P><FORM name=infoform> <P><TABLE BORDER=0> <TR> <TD WIDTH=83> <P>Name: </TD> <TD> <P><INPUT TYPE=text NAME=fullname VALUE=""

SIZE=32> </TD> </TR>

<TR> <TD WIDTH=83> <P>Address: </TD> <TD> <P><INPUT TYPE=text NAME=address VALUE=""

SIZE=32> </TD> </TR> <TR> <TD WIDTH=83> <P>E-mail: </TD> <TD> <P><INPUT TYPE=text NAME=email VALUE=""

SIZE=32> </TD> </TR> <TR> <TD WIDTH=83> <P><INPUT TYPE=button VALUE="Submit"

onclick="verify()"> </TD> <TD> <P><INPUT TYPE=reset VALUE="Clear Your

Information"> </TD> </TR> <TR> <TD COLSPAN=2> <P><TEXTAREA NAME=display ROWS=5 COLS=41

WRAP=virtual></TEXTAREA> </TD> </TR> </TABLE>

</FORM> </BODY> </HTML>

html javascript and css

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