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This article mainly introduces the use of Vue data monitoring method watch. It is quite good. Now I will share it with you and give it as a reference. Let’s take a look together
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 The 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>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 upon 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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