This time I will bring you a detailed explanation of the use of the Vue data monitoring watch method. What are the precautions for the Vue data monitoring watch method? 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 functionWhen 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>
//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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