JavaScript forEach how to pass value

Question

const numbers = [65, 44, 12, 4];
const tPass = 'hello';
numbers.forEach(myFunction)

function myFunction(item, index) {
  console.log(item);
}

how do i pass tPass value to myFunction, and display for example console.log(tPass + item);

tpass should be already available there. can you please read about scope in javascript — abhishek sahu, Dec 21 '21 at 16:51
What happens when you try to do the exact thing you're asking? — David, Dec 21 '21 at 16:53
Replace `numbers.forEach(myFunction)` with `numbers.forEach((item, index) => myFunction(item, index, tPass))` — Lennholm, Dec 21 '21 at 16:56
[You can pass additional parameters](https://stackoverflow.com/questions/40802071/pass-an-extra-argument-to-a-callback-function), but in this scenario it doesn't really make sense. — Ivar, Dec 21 '21 at 16:58

score 2 · Accepted Answer · answered Dec 21 '21 at 16:56

2

You could use bind:

const numbers = [65, 44, 12, 4];
const tPass = 'hello';
numbers.forEach(myFunction.bind(null, tPass))

function myFunction(tPass, value, index) {
  console.log(tPass, value, index);
}

answered Dec 21 '21 at 16:56

Jean Will

543
3
11

score 1 · Answer 2 · answered Dec 21 '21 at 17:04

The forEach method skeleton can have the initial (item, index) parameters as you wrote before. And so in order to modify that, you have to make sure that you are always returning a function with the same argument structure.

Meaning: You declare a higher order function which we'll call myHigherFunction. myHigherFunction takes "tpas" and applys the logic for myFunction inside it, and returns it at the end. Finally, you pass tPass to myHigherFunction.

So the code becomes as follows:

const numbers = [65, 44, 12, 4];
const tPass = 'hello';
numbers.forEach(myHigherFunction(tPass))

function myHigherFunction(tPass){
  
  function myFunction(item, index) {
    console.log(tPass + item);
  }
  return myFunction
}

Remember to always return a function with the required skeleton (initial 2 parameters).

What @JeanW did is basically a built in JS method for the same thing. — Kamar, Dec 21 '21 at 17:06

JavaScript forEach how to pass value

2 Answers2