vue 无限滚动加载指令

Vue.directive('scroll', {
    // 当被绑定的元素插入到 DOM 中时……
    bind: function(el, binding, vnode) {
        el.style.overflow = 'auto'
        let distance = 10;
        let _this = this;
        let busy = el.getAttribute("busy");
        let goOn = false;
        if (busy) {
            vnode.context.$watch(busy, function(value) {
                goOn = value;
            });
        }
        el.addEventListener("scroll", function() {
            var scrollTop = el.scrollTop;
            var viewHeight = el.offsetHeight;
            var innerHeight = 0
            el.children.forEach((item) => {
                innerHeight += item.offsetHeight
            })
            if (innerHeight - (scrollTop + viewHeight) <= distance) {
                if (goOn) {
                    binding.value.call(_this)
                    goOn = false
                }
            }
        }, false)
    }
})