class Scroll {
  static get top() {
    return Math.max(document.documentElement.scrollTop || document.body.scrollTop);
  }
  static get clientHeight() {
    return Math.max(document.documentElement.clientHeight || document.body.clientHeight);
  }
  static get clientWidth() {
    return Math.max(document.documentElement.clientWidth || document.body.clientWidth);
  }
  static get height() {
    return Math.max(document.documentElement.scrollHeight || document.body.scrollHeight);
  }
  static get width() {
    return Math.max(document.documentElement.scrollWidth || document.body.scrollWidth);
  }
  static get bottom() {
    return Scroll.height - Scroll.clientHeight - Scroll.top;
  }
}

const on = (function () {
  if (document.addEventListener) {
    return function (element, event, handler) {
      if (element && event && handler) {
        element.addEventListener(event, handler, false);
      }
    };
  } else {
    return function (element, event, handler) {
      if (element && event && handler) {
        element.attachEvent('on' + event, handler);
      }
    };
  }
})();

/**
 * 降低事件执行频率
 */
const downsampler = (function () {
  let result = null;
  return function (time, func) {
    if (!result) {
      result = setTimeout(function () {
        func();
        result = null;
      }, time);
    }
  }
})();

Vue.directive("infinite-scroll", {
  bind(el, binding, vnode) {
    on(window, 'scroll', function () {
      if (typeof binding.value === "function" && Scroll.bottom <= 50) {  // 小于50就触发
        downsampler(50, binding.value); // 降低触发频率
      }
    })
  }
});

<div class="app" v-infinite-scroll="coupon">
    <template v-for="item in goods">
      <p>{{item}}</p>
   </template>
</div>
    let v = new Vue({
      el: ".app",
      data(){
        return {
          goods:[]
        }
      },
      methods: {
        coupon() {
          this.goods.push("你呵呵")
        }
      }
    })