防抖与节流

节流

简单实现;
function debounce(fn, options) {
  const { delay } = options;
  let timer;

  return function (...args) {
    if (timer) {
      clearTimeout(timer);
    }
    timer = setTimeout(() => {
      fn.call(this, ...args);
      timer = null;
    }, wait);
  };
}

// -----------立即执行防抖函数
function debounce2(fn, delay) {
  let timer;

  return function () {
    let args = arguments;
    if (timer) clearTimeout(timer);

    let callNow = !timer;
    timer = setTimeout(() => {
      timer = null;
    }, delay);
    if (callNow) {
      fn(args);
    }
  };
}
// ----------立即执行防抖函数+普通防抖
function debounce3(fn, delay, immediate) {
  let timer;

  return function () {
    let args = arguments;
    let _this = this;
    if (timer) clearTimeout(timer);

    if (immediate) {
      let callNow = !timer;
      timer = setTimeout(() => {
        timer = null;
      }, delay);

      if (callNow) {
        fn.apply(_this, args);
      }
    } else {
      timeout = setTimeout(() => {
        func.apply(_this, arguments);
      }, delay);
    }
  };
}

节流

// ---------------------------------------------------------节流 ，时间戳版

function throttle(fn, wait) {
  let previous = 0;
  return function () {
    let now = Date.now();
    let _this = this;
    let args = arguments;
    if (now - previous > wait) {
      fn.apply(_this, arguments);
      previous = now;
    }
  };
}

// ---------------------------------------------------------节流 ，定时器版
function throttle2(fn, wait) {
  let timer;
  return function () {
    let _this = this;
    let args = arguments;
    if (!timer) {
      timer = setTimeout(() => {
        timer = null;
        fn.apply(_this, arguments);
      }, wait);
    }
  };
}