How to return an array of numbers that represent lengths of elements string?

If an array was: [‘hey’, ‘you’, ‘muddy’] The expected output should be: [3, 3, 5]

This is what I have so far:

function lengths(arr) {
  numbersArray = [];
  for (var i = 0; i < arr.length; i++) {
    numbersArray = arr[i].length;
  }
}

Any help would be much appreciated.

Answer

You need to push the length of every item (using Array#push) and return the array in the end:

function lengths(arr) {
  const numbersArray = [];
  for (let i = 0; i < arr.length; i++) {
    numbersArray.push(arr[i].length);
  }
  return numbersArray;
}

console.log( lengths(['hey', 'you', 'muddy']) );

Another solution using Array#map:

function lengths(arr) {
 return arr.map(str => str.length);
}

console.log( lengths(['hey', 'you', 'muddy']) );