Count substrings of string

Angelos Chalaris · JavaScript, String, Algorithm · Jan 7, 2021

Counts the occurrences of a substring in a given string.

  • Use Array.prototype.indexOf() to look for searchValue in str.
  • Increment a counter if the value is found and update the index, i.
  • Use a while loop that will return as soon as the value returned from Array.prototype.indexOf() is -1.
const countSubstrings = (str, searchValue) => {
  let count = 0,
    i = 0;
  while (true) {
    const r = str.indexOf(searchValue, i);
    if (r !== -1) [count, i] = [count + 1, r + 1];
    else return count;
  }
};
countSubstrings('tiktok tok tok tik tok tik', 'tik'); // 3
countSubstrings('tutut tut tut', 'tut'); // 4

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