JavaScript Variables
A JavaScript variable is simply a name of storage location. There are two types of variables in JavaScript : local variable and global variable.
There are some rules while declaring a JavaScript variable (also known as identifiers).
- Name must start with a letter (a to z or A to Z), underscore( _ ), or dollar( $ ) sign.
- After first letter we can use digits (0 to 9), for example value1.
- JavaScript variables are case sensitive, for example x and X are different variables.
Correct JavaScript variables
var x = 10;
var _value="sonoo";
Incorrect JavaScript variables
Example of JavaScript variable
Let’s see a simple example of JavaScript variable.
See this example:
<script>
var x = 10;
var y = 20;
var z=x+y;
document.write(z);
</script>
Output:
JavaScript local variable
A JavaScript local variable is declared inside block or function. It is accessible within the function or block only. For example:
<script>
function abc(){
var x=10;//local variable
}
</script>
Or,
<script>
If(10<13){
var y=20;//JavaScript local variable
}
</script>
JavaScript global variable
A JavaScript global variable is accessible from any function. A variable i.e. declared outside the function or declared with window object is known as global variable. For example:
<script>
var data=200;//gloabal variable
function a(){
document.writeln(data);
}
function b(){
document.writeln(data);
}
a();//calling JavaScript function
b();
</script>
