Detailed explanation of the use of watch method in Vue-JS Tutorial-php.cn

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Detailed explanation of the use of watch method in Vue

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Apr 28, 2018 am 09:58 AM

watch method Detailed explanation

This time I will bring you a detailed explanation of the use of the watch method in Vue. What are the precautions when using the watch method in Vue. The following is a practical case, let's take a look.

The watch itself is easy to understand. The watch is responsible for associating the data in the view with a certain function

When the data in the Vue view changes, the associated function will be executed

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>监听方法watch的使用</title>
  <script src="https://cdn.bootcss.com/vue/2.5.16/vue.js"></script>
</head>
<body>
  <p id="root"></p>
  <script>
    var vm = new Vue({
      el: "#root",
      data: { obj: {name: "zhaoolee", age: 12} , tel:6666666},
      template: `<p><p>姓名: {{obj.name}}</p>
        <p>电话: {{tel}}</p>
        <input type="text" v-model="obj.name">
        <input type="text" v-model="tel"></p>`,
      watch: {
        obj: {
         handler(){
           console.log("obj被改变");
         },
          // 页面加载之初先执行一次handle
         immediate: true,
          // 深度检查属性,即使对象内部的属性值改变, 也能检测到(比较消耗性能)
         deep: true
        },
        "obj.name": {
          handler(){
            console.log("=>obj.name被改变");
          }
        },
        tel:{
          handler(){
            console.log("tel被改变");
          }
        }
      }
    })
  </script>
</body>
</html>

Copy after login

corresponds to an object, the key is the observation expression, and the value is the corresponding callback. The value can also be a method name, or an object containing options. Call $watch() for each key during instantiation;

//使用官方vue-cli脚手架书写
<template>
　　//观察数据为字符串或数组
　　 <input v-model="example0"/>
　　 <input v-model="example1"/>
　　/当单观察数据examples2为对象时，如果键值发生变化，为了监听到数据变化，需要添加deep:true参数
　　 <input v-model="example2.inner0"/>
</template>
<script>
　　 export default {
　　　　　　data(){
　　　　　　　　return {
　　　　　　　　　　example0:"",
　　　　　　　　　　example1:"",
　　　　　　　　　　example2:{
　　　　　　　　　　　　inner0:1,
　　　　　　　　　　　　innner1:2
　　　　　　　　　　}
　　　　　　　　}
　　　　　　},
　　　　　　watch:{
　　　　　　　　example0(curVal,oldVal){
　　　　　　　　　　console.log(curVal,oldVal);
　　　　　　　　},
　　　　　　　　example1:'a'，//值可以为methods的方法名
　　　　　　　　example2:{
　　　　　　　　　//注意：当观察的数据为对象或数组时，curVal和oldVal是相等的，因为这两个形参指向的是同一个数据对象
　　　　　　　　　　handler(curVal,oldVal){
　　　　　　　　　　　　conosle.log(curVal,oldVal)
　　　　　　　　　　},
　　　　　　　　　　deep:true
　　　　　　　　}
　　　　　　},
　　　　　　methods:{
　　　　　　　　a(curVal,oldVal){
　　　　　　　　　　conosle.log(curVal,oldVal)
　　　　　　　　}
　　　　　　}
  }
</script>

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I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the PHP Chinese website!

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