Function debouncing

debounce.js

function debounce (fn, ms, immediate = false) {
  let timeout;

  return function () {
    const call = () => {
      timeout = null;
      if (!immediate) fn.apply(this, arguments);
    };

    const now = immediate && !timeout;

    clearTimeout(timeout);
    timeout = setTimeout(call, ms);
    if (now) fn.apply(this, arguments);
  };
}