1、防抖、节流

// 截流与防抖
/**
 * @desc 防抖
 * @param {number} delay 延迟时间
 * @param {func} cb 回调
 */
export function debounce(delay,cb) {
  let timeoutID;
  function wrapper() {
    const self = this;
    const args = arguments; 
    function exec() {
      cb.apply(self, args);
    }
    clearTimeout(timeoutID);
    timeoutID = setTimeout(exec, delay);
  }
  return wrapper;
}

/**
 * @desc 截流
 * @param {number} delay 延迟时间
 * @param {func} cb 回调
 */
export function throttle(delay,cb){
  let timeoutID;
  let lastExec = 0;
  function wrapper() {
    const self = this;
    const args = arguments; 
    const elapsed = Number(new Date()) - lastExec;
    function exec() {
      lastExec = Number(new Date());
      cb.apply(self, args);
    }
    clearTimeout(timeoutID);
    if (elapsed > delay) {
      exec();
    } else {
      timeoutID = setTimeout(exec, delay - elapsed);
    }
  }
  return wrapper;
}