How do I utilize the index for my callback?

December 6, 2022

Going through some practice problems and can’t figure out how correctly callback. It returns "

let myForEach = function(array, cb) {
  for (let j = 0; j < array.length; j++) {
    cb(array[j])
  }
};

myForEach(['a', 'b', 'c'], function(el, i) {
  console.log(el + ' is at index ' + i);
});


// expected return "a is at index 1"
// actual return "a is at index undefined"

I tried to call i as an extra argument, and tried to use this.i, call it within the scope of the cb, all either return undefined or are ignored.

>Solution :

You can utilize the index for the callback by passing it in as a second argument:

let myForEach = function(array, cb) {
  for (let j = 0; j < array.length; j++) {
    cb(array[j], j)
  }
};

myForEach(['a', 'b', 'c'], function(el, i) {
  console.log(el + ' is at index ' + i);
});

// expected return "a is at index 0"
// actual return "a is at index 0"