函数防抖和函数节流

function debounce(fn, delay, triggerNow) {
  let t = null,
    res;

  const debounced = function () {
    let _self = this,
      args = arguments;

    if (t) {
      clearTimeout(t);
    }

    if (triggerNow) {
      let exec = !t;
      t = setTimeout(function () {
        t = null;
      }, delay);
      if (exec) {
        res = fn.apply(_self, args);
      }
    } else {
      t = setTimeout(function () {
        res = fn.apply(_self, args);
      }, delay);
    }
    return res;
  };

  debounced.remove = function () {
    clearTimeout(t);
    t = null;
  };
  return debounced;
}

function throttle(fn, delay) {
  let t = null,
      begin = new Date().getTime();
  return function () {
    var _self = this,
      args = arguments,
      cur = new Date().getTime();
    clearTimeout(t);

    if (cur - begin >= delay) {
      fn.apply(_self, args);
      begin = cur;
    } else {
      t = setTimeout(function () {
        fn.apply(_self, args);
      }, delay);
    }
  }
}