Javascript part two

Variable

What is variable?

                 In programming, a variable is value that can change, depending on condition or no information passed to the program.

                 In object-orianted programming, each object contains the data variables of the class it is an instance of. The objects's method's are design to handle the actual values that are supplied to the object when the object is being used.

Variable in javascript

                  Variable types are not important in JavaScript. They may be interchanged as necessary. This means that if a variable is a string one minute, it can be an integer the next. The basic variable types are:

character

               'a' or '@' or 'k' etc.

string

               'hdttgs 8 -46hs () Get the idea'

integer

               0 or 1 or 2 or 3 or 4 etc. or -1 or -2 or -3 or -4 etc.

float (or double)

               23.546 or -10.46

boolean

               true or false

function

              A function; see the section on Functions

object

              An object; see the section on Object oriented programming

array

              A type of object that can store variables in cells (see below)

regular expression

              A pattern that can be used to match strings or substrings

undefined

             A variable that has not been given a value yet

 JavaScript Variable Scope

      The scope of a variable is the region of your program in which it is defined. JavaScript variables have only two scopes.

• Global Variables − A global variable has global scope which means it can be defined anywhere in your JavaScript code.

• Local Variables − A local variable will be visible only within a function where it is defined. Function parameters are always local to that function.

      Within the body of a function, a local variable takes precedence over a global variable with the same name. If you declare a local variable or function parameter with the same name as a global variable, you effectively hide the global variable. 

Example

<script type="text/javascript">

   <!--

      var myVar = "global"; // Declare a global variable

      function checkscope( ) {

         var myVar = "local";  // Declare a local variable

         document.write(myVar);

      }

   //-->

</script>