Function calling with constructors in javascript

Question

I have confusion on function calling in javascript,Can some one tell answer for below question ?

**Question 1:**
function A(){


}


function A(){


}

A();

In this case,which function will call?is it first or second function? and why?

**Question 2:**
function A(a){


}


function A(a,b){


}

A();

In this case,which function will call?is it first or second function? and why?

Thanks in advance.

Answer 1

Let's put it in action and see the results:

function A(){
  var el = document.getElementById('test');
  el.innerText  = "First function";
}

function A(){
  var el = document.getElementById('test');
  el.innerText  = "Second function";
}

A();

<div id="test"></div>

As we can see, the second function is the winner. Why? Because when we write it again after a first declaration we just overwrite it really.

As for the second question:

function A(a){
  var el = document.getElementById('test');
  el.innerText  = "First function";
}

function A(a,b){
  var el = document.getElementById('test');
  el.innerText  = "Second function";
}

A();

<div id="test"></div>

As we see, it still executes the second question. That's because javascript isn't a polymorphic language, that is, it cannot have two function with the same name but with different input declarations like java does. We just did the same thing we did above: We overwrite the function A.

PS: If javascript were a polymorphic language (which it isn't), then the second run would return an error because we haven't declared an version of function A that receive 0 variables as input.