an introduction to javascript summarized from chapter 6 of “web programming: building internet...
TRANSCRIPT
An Introduction to JavaScript
Summarized from Chapter 6 of
“Web Programming:
Building Internet Applications”, 3rd Edition
What is JavaScript?
a dynamic, client-side scripting language it is not compiled it is not Java (from Sun)
developed by Netscape originally called LiveScript When Java became popular – Netscape changed
the name to JavaScript open language (no purchasing)
What is JavaScript? (cont.)
Now managed by ECMA (European Computer Manufacturers Association) and adopted by ISO
Since it is a client-side language, it works with a browser
What is JavaScript? (cont.)
Pros form validation (before
sending to a server) calculations create custom HTML on-
the-fly test for plug-ins and other
browser settings (does not work in IE after version 5.0; that function is now handled by ActiveX)
Cons cannot read local files
(files on the client machine)
cannot write local file (except for cookies)
cannot read/write server files
can only close it’s own windows
can only read data from it’s own pages
JavaScript is Object-Oriented (?) Objects are things
In the world (cat, chair, car, etc.) In browsers (window, button, title, etc.)
Objects have properties size, color, and position are all properties Object are said to “have a” property
Object have methods (or functions) these are things that object do click(), open(), selected() are methods
Think of Think of properties as properties as being nounsbeing nouns
Think of Think of methods are methods are being verbsbeing verbs
What is the DOM?
Document Object Model Developed by W3C but implemented differently in
every browser. “The Document Object Model is a platform- and
language-neutral interface that will allow programs and scripts to dynamically access and update the content, structure and style of documents. The document can be further processed and the results of that processing can be incorporated back into the presented page. This is an overview of DOM-related materials here at W3C and around the web.” (http://www.w3.org/DOM/)
objectobject
propertiesproperties
methodsmethods
A Document Tree (node tree)
downloaded from http://www.w3schools.com/htmldom/default.asp
A Worked Example
<html>
<head> <body>
<title> <p>
texttext
“My Page”“This is text on my
page”
<html>
<head>
<title>My Page</title>
</head>
<body>
<p>This is text on my page</p>
</body>
</html>
Hello, world!
Another couple of examples
Conditions (if statements)
In order to validate to In order to validate to XHTML-Strict, you need to XHTML-Strict, you need to
leave out leave out ‘language=“javascript”.‘language=“javascript”.
TRUE partTRUE part
FALSE partFALSE part
Example 6.3.1 A Simple Script (from text) navigator refers to navigator refers to
the browser objectthe browser object
alert creates a pop-up alert creates a pop-up windowwindow
document.write creates document.write creates the content on a web the content on a web
pagepage
onLoad and onUnload onLoad and onUnload are eventsare events
A Simple Script variation
Inside the describe() function, change the document.write lines to display all of the data on a page instead of a pop-up
User InputPrompt the user and Prompt the user and store the input as a store the input as a
variablevariable
You can include this in You can include this in your page to notify the your page to notify the
user that their user that their JavaScript is disabled.JavaScript is disabled.
