JavaScript

An Introduction


 

Part I: Structure of a JavaScript program

 

JavaScript Characteristics
  • scripting language
  • embeded directly inside of the HTML file
  • is interpreted by code in the browser on the client side.
  • because it is downloaded in an uncompress format, you need to be conscience of the size of the code you are downloading.
  • typically used for simple graphical interfaces.
  • simple language that due to some lack of structure for a programmer can be unintuitive...but, for a non-programmer possibly easier than other languages.....really developed for the non-programmer.
  • JavaScript code is surrounded by the following. Note: the code is encodes inside of an HTML comment....this is not require but, good practice in case someone with a very old browser does not recognize JavaScript this will insure it doesn't choke and will display the rest of the HTML.

<SCRIPT Language="JavaScript">

<!--

           THE JavaScript Code GOES HERE

 

// -->

</SCRIPT>
  • Location of Code:
    • if in <HEAD> statement than this is where you will put functions, etc.
    • if in <BODY>, this is where you will put the code that actually executes possibly using funcitons from the code in the <HEAD> portion of the HTML.

 

JavaScript Uses/Capabilities
  • Can generate HTML dynamically.
  • Used for simple user interface interactions: button roll-overs,etc.
  • Can make Java calls directly from JavaScript, to extend the possibilities greatly using Java.
  • Can be used to check data in form before sending off to a CGI-script on the server for processing.

 

JavaScript Basics: Literals, Variables and More

 

 

Next: Objects and Classes, and Functions.