How to call nested function in javascript?

Question

I have two function like this..

function a() {
 function b() {
 alert('reached');
 }
}

how i call function b() from outside of function a()..

• Sinkingpoint: You can't. b is only defined inside the scope of a.
• RBT: Some very good answers in this related post here.

Answer 1

In general, you can't. The point of defining a function inside another function is to scope it to that function.

The only way for b to be accessible outside of a is if (when you call a) you do something inside a to make it available outside of a.

This is usually done to create a closure, so that b could access variables from a while not making those variables public. The normal way to do this is to return b.

function a() {
 var c = 0;
 function b() {
 alert(c++);
 }
 return b;
}
var d = a();
d();
d();
d();
var e = a();
e();
e();
e();

Answer 2

You can rearange your code to this

function a() {
 this.b = function() {
 alert('reached');
 }
}

now instantiate it and run:

c = new a();
c.b();

Answer 3

You will need to return the inner function call.

function a() {
 function b() {
 alert('reached');
 }
 return b();
}

And then you can call this function simply by calling function a like this:

a();

The output will be the required alert.

• Fuzzyma: there is no need to return the return-value of b when you just wanna call it