In-depth understanding of function overloading in JavaScript_javascript skills

There is a special data type in JavaScript---Function type. Each function in JavaScript is an instance of Function type. Since functions are objects, the function name is actually a pointer to the function object and will not be 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 the function name as a pointer to the function helps to 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 with the same name are declared, the latter function overwrites the previous function. The above is equivalent to the following code

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

When creating the second function, the referenced first function variable sum is actually overwritten