<template>
 <div class="sticky" :style="getPosition">
 <div class="sticky-warp">
 <slot></slot>
 </div>
 </div>
</template>

<style scoped lang="less" rel="stylesheet/less">
 .sticky {
 width: 100%;
 .sticky-warp {
 width: 100%;
 background: inherit;
 will-change: change;
 height: inherit;
 top: inherit;
 }
 }
</style>

<script type="text/babel">
 export default {
 data () {
 return {}
 },
 computed: {
 getPosition(){
 var position = this.cssSupport('position', 'sticky') ? 'sticky' : 'relative';
 return 'position:' + position;
 }
 },
 props: {},
 beforeMount () {
 },
 mounted(){
 this.init();
 },
 deactivated(){
 if(this.cssSupport('position', 'sticky')) {
 return;
 }
 /*復位*/
 var elWarp = this.$el.querySelector('.sticky-warp');
 elWarp.position = 'absolute';
 },
 methods: {
 init(){
 if (this.cssSupport('position', 'sticky')) {
 return;
 }
 var el = this.$el, target = this.$el.parentNode,
 elWarp = this.$el.querySelector('.sticky-warp'),
 top = this.getNumberValue(document.defaultView.getComputedStyle(el).top);
 this.addScrollListen(target, (event)=> {
 if (el.getBoundingClientRect().top <= top) {
 elWarp.style.position = 'fixed';
 }
 if (el.getBoundingClientRect().top >= 0 && elWarp.style.position != 'absolute') {
 elWarp.style.position = 'absolute';
 }
 })
 },
 cssSupport: function (attr, value) {
 var element = document.createElement('div');
 if (attr in element.style) {
 element.style[attr] = value;
 return element.style[attr] === value;
 } else {
 return false;
 }
 },
 getNumberValue(pxValue){
 var value = String(pxValue).match(/^\-?\+?[0-9]+/g);
 return value ? Number(value) : undefined;
 },
 addScrollListen(target, cb){
 target.addEventListener('y-scroll', (event)=> {
 cb && cb(event);
 });
 }
 },
 }

 
</script>