Can you use parent function variables inside a returned function in javascript?

Question

Here's the function code:

function TestFunction(number){
  return function(e){
    return `${number}`;
  }
}

When I use it on google's devtools command line it returns:

function(e){
  return `${number}`;
}

So it looks like the function returned is not created with the number I give to TestFunction, instead it takes the string just like it was written. I have tried to use concatenation instead of interpolation but still not working. What can I do?

The value of number is resolved when the function is actually executed. — Felix Kling
– Felix Kling, Commented Dec 14, 2019 at 9:57

Nick · Accepted Answer · 2019-12-14 01:02:04Z

1

There is indeed a closure around the second function, so it will have memory of what num is.

function a(num) {
  return function b() {
    return `${num}`;
  }
}

const c = a(6);

console.log(c());

answered Dec 14, 2019 at 1:02

Nick

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