javascript function with in function in variable

Question

I have a doubt

My Code :-

function f() { 
    var g = function() 
    { 
    return 1;
    } 
    return g; 
  };

How do I can call g? I want to return 1 once and again I want to return g.

I did a Research I found a solution

How we can call g is:-

f()();

Why this is ?? What is f()(); in JavaScript. why not we can achieve this using f.g or something.

How can I return g from the function f ??

Please clarify my doubts ?

Answer 1

How can I return g from that function?

You are returning g from "that function", assuming "that function" is f. Since f returns a function you are able to invoke the return value with f()(). It's pretty much the same as this:

var returnedFunction = f();
returnedFunction();

why not we can achieve this using f.g or something?

Because g is not a property of f. I'm not entirely sure what you're aiming for, but perhaps you wanted f to be a constructor, and instances of it to have a method g?

function f() {
    // Constructor function
}
f.prototype.g = function () {
    // Method
};
var myF = new f();
myF.g(); // Now `g` is accessible as a property of the instance

You could alternatively have intended g to be a static property of f:

function f() {
    // JS has first-class functions so you can set properties on them
}
f.g = function () {
    // Static method of `f`
};
f.g();

Answer 2

Your f() is returning a function and the second () means you are calling that function.

Think of it like this

var g = f();
g();

Except when you do f()() you are basically inlining the variable.

If you wanted to call it using f.g() you would need to declare f as an object or add g as a property.

function f() {
  this.g = function() {
    return 1;
  };
}
new f().g();

or

var f = {
  g: function() {
    return 1;
  }
}
f.g();

But I am not 100% what it is you are trying to accomplish.