Misago/frontend/src/utils/string-count.js

export default function(string, subString) {
  string = (string + "").toLowerCase();
  subString = (subString + "").toLowerCase();

  if (subString.length <= 0) return 0;

  let n = 0;
  let pos = 0;
  let step = subString.length;

  while (true) {
    pos = string.indexOf(subString, pos);
    if (pos >= 0) {
      n += 1;
      pos += step;
    } else {
      break;
    }
  }

  return n;
}