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JavaScript

  1. Introduction

    The Language

  2. Starting
  3. Variables
  4. Operators
  5. Control and Loops
  6. Functions
  7. Predefined Functions
  8. Events

    Objects

  9. Object Creation and Use
  10. Object Hierarchy

    Independent Objects

  11. Array Object
  12. Date Object
  13. Math Object
  14. Number and Boolean Object
  15. String Object

    Main Object

  16. Navigator Object

    Navigator Objects

  17. Window Object
  18. MimeType Object
  19. Plugin Object

    Window Sub Objects

  20. Document Object
  21. Location Object
  22. History Object
  23. Frame Object

    Document Sub Objects

  24. Anchor Object
  25. Applet Object
  26. Area Object
  27. Form Object
  28. Image Object
  29. Layer Object
  30. Link Object

    Form Sub Objects

  31. Button Object
  32. Checkbox Object
  33. FileUpload Object
  34. Hidden Object
  35. Option Object
  36. Password Object
  37. Radio Object
  38. Reset Object
  39. Select Object
  40. Submit Object
  41. Text Object
  42. Textarea Object

    More

  43. Handling Cookies
  44. Style Attributes

    Examples

  45. Simple Examples
  46. Handling Form Input
  47. Individual Hit Counter
  48. Redirecting based on Cookies

    Appendices

  49. Terms
  50. Credits

CGI
Web Tech
Independent
Home

Starting JavaScript

Embedding Script

Javascript statements are hidden in HTML comments to prevent incorrect interpretation by older browsers that do not recognize JAVA script. An example HTML document with embedded JAVA script is shown. 

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<title>An Example of JavaScript code</title>
<head>
<body>
<script language="JavaScript">
<!-- Use the HTML comment to hide JavaScript from old browsers
document.write("This text was written using JavaScript.")
// End hiding JavaScript -->
</script>
<NOSCRIPT>
You see this if your browser won't run JavaScript.
</NOSCRIPT>
</body>
</html>

Note that there are two tags used to implement this script example:

  • SCRIPT - The area between the <SCRIPT> and the </SCRIPT> tags defines the script program.
    • language - Defines the script language. Choices are JavaScript and VBScript.
    • SRC - Defines an external file containing the source code of the JavaScript. It may be a URL with the complete path to the script which may reside at another website. An example is:

      <script language="JavaScript" SRC="testscript.js">

  • NOSCRIPT - The area between the <NOSCRIPT> and the </NOSCRIPT> tag is run by browsers that can't run JAVA script or have the feature turned off.


GlobalSpec - The Engineering Search Engine

Other Script embedding methods and information

  • Entities which begin with "&{" and end with "};" Example: 
    <html>
<head>
<title>The entity method of using JavaScript.</title>
<script language="JavaScript"><!--
CGILink="http://www.ctdp.tripod.com/independent/web/cgi/index.html"
// -->
</script>
</head>
<body>
<A HREF="&{CFILink};">Go to CGI Section.</A>
</body>
</html>
  • Comments are started with "//" for a single line, along with the "/*" to start a comment and "*/" to end a comment for multiple lines. The comments work the same as in C++.
  • In JAVA, a variable must be defined before it is used, therefore it is a common practice to place JavaScript definitions in the header section of an HTML file. The example below will randomly select and display a greeting in an HTML header of size three. 
    <HTML>
<HEAD>
<TITLE>Common JavaScript definition practice</TITLE>
<SCRIPT language="JavaScript">
<!--
Greeting = new Array(4); 
Greeting[0] = "have a nice day."
Greeting[1] = "it's a great day."
Greeting[2] = "have a great day!"
// -->
</SCRIPT>
</HEAD>
<BODY>
<CENTER><H1>This is a Greeting Example</H1></CENTER>
<SCRIPT language="JavaScript">
<!--
i1 = Math.round(Math.random() * 3)
document.write(("<H3>Hi, " + Greeting[i1] + "</H3>\n")
// -->
</SCRIPT>
</BODY>
</HTML>
  • Special characters include:
    • \b - backspace
    • \f - Form feed
    • \n - New line
    • \r - Carriage return
    • \t - Tab