JavaScript Variables

A variable is something that can change ("vary"). Variables can be thought of as "containers" for values used by the programme.

Rules for JavaScript Variable Names: (From: Michael Moncur, 1996, JavaScript 1.1, p31)

Variables may contain any letter of the alphabet or the digits 0-9 and the 'underscore" character (ie "_").
Variable names may not contain spaces or any of the 'punctuation' characters (eg comma, full stop, etc)
The first character of a variable name can NOT be a numeral.
Variable names are case-sensitive. eg MyAnswer, myanswer and MYANSWER are treated as different variable names.
There is no official limit to the length of a variable name. It must fit on one line.

Typical Variable Assignments:

age = 52;
MySurname = 'Featherstone';
WeeklyAverage = base * mean / 27;

Variable Scope:

Variables may be either Global, or Local.

Local variables are available only within the section of code in which they were defined. Changes to Local variables are not reflected 'outside' their area of definition.
Global variables are available to other JavaScript code.

Generally, variables declared as "var" are Global variables. Variables declared inside a function as "var" are local to the function. Variables defined inside a function without the "var" are Global variables.

<HTML>
<HEAD>
<TITLE>Variable Scope</TITLE>
<SCRIPT LANGUAGE= "JavaScript">
var count = 22;                           //GLOBAL
var age = 67;                              //GLOBAL
function audit( ) {
   code = 23;                                //GLOBAL
   var adjust = 7.5;                        //LOCAL
   audited = (count * age)/code + adjust;
   return audited;
}
</SCRIPT>
</HEAD>
<BODY>
...
...
...
</BODY>
</HTML>

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