const debounce = (fn, delay, immediate) => {
  let timeout;
  if (immediate) {
    let locked = false;
    return function(...args) {
      clearTimeout(timeout);
      if (!locked) {
        fn.apply(this, arguments);
        locked = true;
      }
      timeout = setTimeout(() => {
        locked = false;
      }, delay);
    }
  }
  else return function(...args) {
    clearTimeout(timeout);
    timeout = setTimeout(() => {
      fn.apply(this, arguments);
    }, delay);
  }
}