$nextTick
data改變之後,DOM不會立刻渲染,獲取不到最新的DOM節點;
$nextTick會在DOM渲染之後被觸發,以獲取最新DOM節點
<template>
<div>
<ul ref="ul1">
<li v-for="(item,index) in list" :key="index">{{item}}</li>
</ul>
<button @click="add">添加項</button>
</div>
</template>
<script>
export default {
data() {
return {
list: ["a", "b", "c"],
};
},
methods: {
add() {
this.list.push(Date.now());
this.list.push(Date.now());
this.list.push(Date.now());
const ulElem = this.$refs.ul1; //獲取ul的DOM節點
console.log(ulElem.childNodes.length); //此時data改變之後,DOM不會立刻渲染,獲取不到最新的DOM節點
// $nextTick會在DOM渲染之後被觸發,以獲取最新DOM節點
this.$nextTick(() => {
const ulElem = this.$refs.ul1; //獲取ul的DOM節點
console.log(ulElem.childNodes.length); //$nextTick會在DOM渲染之後被觸發,此時已經是最新的DOM節點
});
// 1. 異步渲染,$nextTick 待DOM渲染完再回調
// 2. 頁面渲染是,會將data的修改做整合,多次data修改只會渲染一次
},
},
};
</script>