indexOfSubstrings javascript Code Snippet in 2025

Finds all the indexes of a substring in a given string.

• Use Array.prototype.indexOf() to look for searchValue in str.
• Use yield to return the index if the value is found and update the index, i.
• Use a while loop that will terminate the generator as soon as the value returned from Array.prototype.indexOf() is -1.

const indexOfSubstrings = function* (str, searchValue) {
  let i = 0;
  while (true) {
    const r = str.indexOf(searchValue, i);
    if (r !== -1) {
      yield r;
      i = r + 1;
    } else return;
  }
};

[...indexOfSubstrings('tiktok tok tok tik tok tik', 'tik')]; // [0, 15, 23]
[...indexOfSubstrings('tutut tut tut', 'tut')]; // [0, 2, 6, 10]
[...indexOfSubstrings('hello', 'hi')]; // []