export function throttle(fun, delay) {
  let last, deferTimer;
  return function (args) {
    let that = this;
    let _args = arguments;
    let now = +new Date();
    if (last && now < last + delay) {
      clearTimeout(deferTimer);
      deferTimer = setTimeout(() => {
        last = now;
        fun.apply(that, _args);
      }, delay);
    } else {
      last = now;
      fun.apply(that, _args);
    }
  };
}