Function within another function in javascript

Question

I was trying to call another function inside function iseven(n):

function iseven(n) {
    function remainder(n) {
        if (n%2==0) {
            return true;
        } else {
            return false;
        }
    }
}
console.log(iseven(4));

It returns undefined.

a right way to do this:

function a(x) {    // <-- function
  function b(y) { // <-- inner function
    return x + y; // <-- use variables from outer scope
  }
  return b;       // <-- you can even return a function.
}
console.log(a(3)(4));

nested functions JS

You have a function in a function. The outer one does not return anything. What did you want to do with 2 functions? — trincot, Mar 08 '18 at 19:37

Simon Franzen · Answer 1 · 2018-03-08T20:26:21.497

2

Try

function iseven(n) { return n % 2 === 0; }

edited Mar 08 '18 at 20:26

answered Mar 08 '18 at 19:40

Simon Franzen

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if you expect it to return a `boolean`, i would do `function iseven(n) { return n % 2 === 0; }` but that's just being picky cause `0` and `1` that your functions returns are falsy and truthy values respectively – Rico Kahler Mar 08 '18 at 19:43
You are right @RicoKahler ! I will updated my answer – Simon Franzen Mar 08 '18 at 20:26
@nahu did my answer help you ? – Simon Franzen Mar 11 '18 at 13:48

Terry Lennox · Answer 2 · 2018-03-08T19:49:11.883

2

You want something more like this

function iseven(n)  { 
    if (n%2==0) { 
        return true; } 
    else { 
        return false; 
    } 
}

console.log(iseven(4));

And something a bit more succinct:

function isEven(n) {
   return n % 2 === 0;
}

Not quite sure why the original was structure that way..

edited Mar 08 '18 at 19:49

answered Mar 08 '18 at 19:40

Terry Lennox

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i would prefer the [strict equality operator](https://stackoverflow.com/questions/359494/which-equals-operator-vs-should-be-used-in-javascript-comparisons) but that's more of a style thing in the case of your example – Rico Kahler Mar 08 '18 at 19:45

score 1 · Accepted Answer · answered Mar 08 '18 at 19:45

Your Main function iseven() does not return anything. Based on your code it should return false. Here's the fix:

function iseven(n) { 
    function remainder(n) { 
        if (n%2==0) { 
            return true; 
        } 
        else { 
            return false; 
        } 
    }
    //iseven() should return something
    return false; 
}
console.log(iseven(4));

Function within another function in javascript

3 Answers3