JavaScript Global Variable

A JavaScript global variable is declared outside the function or declared with window object. It can be accessed from any function.

Let’s see the simple example of global variable in JavaScript

<script>  

var value=50;//global variable  

function a(){  

alert(value);  

}  

function b(){  

alert(value);  

}  

</script>

Declaring JavaScript global variable within function

To declare JavaScript global variables inside function, you need to use window object. For example:

window.value=90;  

Now it can be declared inside any function and can be accessed from any function. For example:

function m(){  

window.value=100;//declaring global variable by window object  

}  

function n(){  

alert(window.value);//accessing global variable from other function  

}

Internals of global variable in JavaScript

When you declare a variable outside the function, it is added in the window object internally. You can access it through window object also. For example:

var value=50;  

function a(){  

alert(window.value);//accessing global variable