手写防抖节流

防抖

function debounce(fn, delay) {
  let timer = null;

  return function () {
    let context = this,
      args = [...arguments];
    if (timer) {
      clearTimeout(timer);
      timer = null;
    }
    timer = setTimeout(() => fn.apply(context, args), delay);
  };
}

节流

function throttle(fn, delay) {
  let preTime = Date.now();

  return function () {
    let context = this,
      args = [...arguments],
      nowTime = Date.now();

    if (nowTime - preTime > delay) {
      preTime = nowTime;
      fn.apply(context, args);
    }
  };
}

function throttle(fn, delay) {
  let timer = null;

  return function () {
    let context = this,
      args = [...arguments];
    if (!timer) {
      timer = setTimeout(() => {
        fn.apply(context, args);
        timer = null;
      }, delay);
    }
  };
}