How can I log the index of each array item?

Question

I'm a beginner and struggling with this exercise. Can anyone tell me why the console is logging the index of both characters as 1. I want it to log the character 'a' every time it appears in the word. So for example, if we ran the function with the word ‘Saturday’ and ‘a’ as below, it should log an array [1,6]. Instead it is logging [1, 1].

const subLength = (word, letter) => {
  let wordArray = word.split("");
  let indexArray = []
  for (i = 0; i < wordArray.length; i++) {
    if (wordArray[i] === letter) {
      indexArray.push(wordArray.indexOf(letter));
    }
  }
  console.log(indexArray);
}


subLength('Saturday', 'a');

indexOf() always returns the index of the first element that matches. You should rather just push i. indexArray.push(i) — pilchard
– pilchard, Commented May 10, 2021 at 20:42
Why use indexOf at all? i is already the index you want. — VLAZ
– VLAZ, Commented May 10, 2021 at 20:44
btw, why do you split the string? you could iterate the string without splitting/taking an array. — Nina Scholz
– Nina Scholz, Commented May 10, 2021 at 20:47
@NinaScholz I'm not sure, I think I did it without splitting the string first and something wasn't working. Fixing it probably had nothing to do with splitting it into a string but that's just the way I worked through it. I'll learn. Thanks for your answer! — NicolaHearn
– NicolaHearn, Commented May 13, 2021 at 12:42

Nina Scholz · Accepted Answer · 2021-05-10 20:52:23Z

2

You could take the index i from the loop directly.

String#indexOf returns the first found index, but if you take an index as second parameter it searches from this position.

const subLength = (word, letter) => {
  let wordArray = word.split("");
  let indexArray = [];
  for (let i = 0; i < wordArray.length; i++) { // take let here too
    if (wordArray[i] === letter) {
      indexArray.push(i);
    }
  }
  console.log(indexArray);
}

subLength('Saturday', 'a');

An approach without using split.

const
    subLength = (word, letter) => {
        let indexArray = [];
        for (let i = 0; i < word.length; i++) {
            if (word[i] === letter) indexArray.push(i);
        }
        console.log(indexArray);
    };

subLength('Saturday', 'a');

edited May 10, 2021 at 20:52

answered May 10, 2021 at 20:43

Nina Scholz

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1 Comment

NicolaHearn Over a year ago

Amazing, thanks. I got confused because I tried indexArray.push(wordArray[i]) previously and it was only logging the actual letters not the indexes (indices??) Thanks for answering so quickly!

Unmitigated · Accepted Answer · 2021-05-10 21:02:25Z

0

A simpler method would be to filter over the indexes.

const subLength = (word, letter) => [...Array(word.length).keys()]
  .filter(i => word[i] === letter);
console.log(subLength('Saturday', 'a'));

answered May 10, 2021 at 21:02

Unmitigated

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