There is a special data type in JavaScript, the Function type, and every Function in JavaScript is an instance of the Function type. Because functions are objects, the function name is actually a pointer to a function object and is not bound to a function.

<pre name="code" class="html">function sum(num1,num2)
{
return num1 +num2;
}

alert(sum(10,10)); //20
var other = sum;
alert(other(10,10)); //20
sum = null;
alert(other(10,10)); //20

Using function names as Pointers to functions helps you understand why there is no concept of function overloading in ECMAScript

function sum(num1)
{
return num1 +100;
}
function sum(num1)
{
return num1 +200;
}
alert(sum(200)); //400

Although two functions of the same name are declared, the following function overrides the previous function, which is equivalent to the following code

function sum(num1)
{
return num1 +100;
}
sum = function(num1)
{
return num1 +200;
}
alert(sum(200)); //400