生命周期：Vue 实例从开始创建、初始化数据、编译模板、挂载Dom→渲染、更新→渲染、卸载等一系列过程，我们称这是 Vue 的生命周期，各个阶段有相对应的事件钩子
生命周期图示
生命周期钩子
beforeCreate
created
beforeMount
mounted
beforeUpdate
updated
beforeDestroy
destroyed
直接借用代码直观显示
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<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta http-equiv="X-UA-Compatible" content="ie=edge"> <title>vue生命周期学习</title> <script src="https://cdn.bootcss.com/vue/2.4.2/vue.js"></script> </head> <body> <div id="app"> <h1>{{message}}</h1> </div> </body> <script> var vm = new Vue({ el: '#app', data: { message: 'Vue的生命周期' }, beforeCreate: function() { console.group('------beforeCreate创建前状态------'); console.log("%c%s", "color:red" , "el : " + this.$el); //undefined console.log("%c%s", "color:red","data : " + this.$data); //undefined console.log("%c%s", "color:red","message: " + this.message) }, created: function() { console.group('------created创建完毕状态------'); console.log("%c%s", "color:red","el : " + this.$el); //undefined console.log("%c%s", "color:red","data : " + this.$data); //已被初始化 console.log("%c%s", "color:red","message: " + this.message); //已被初始化 }, beforeMount: function() { console.group('------beforeMount挂载前状态------'); console.log("%c%s", "color:red","el : " + (this.$el)); //已被初始化 console.log(this.$el); console.log("%c%s", "color:red","data : " + this.$data); //已被初始化 console.log("%c%s", "color:red","message: " + this.message); //已被初始化 }, mounted: function() { console.group('------mounted 挂载结束状态------'); console.log("%c%s", "color:red","el : " + this.$el); //已被初始化 console.log(this.$el); console.log("%c%s", "color:red","data : " + this.$data); //已被初始化 console.log("%c%s", "color:red","message: " + this.message); //已被初始化 }, beforeUpdate: function () { console.group('beforeUpdate 更新前状态===============》'); console.log("%c%s", "color:red","el : " + this.$el); console.log(this.$el); console.log("%c%s", "color:red","data : " + this.$data); console.log("%c%s", "color:red","message: " + this.message); }, updated: function () { console.group('updated 更新完成状态===============》'); console.log("%c%s", "color:red","el : " + this.$el); console.log(this.$el); console.log("%c%s", "color:red","data : " + this.$data); console.log("%c%s", "color:red","message: " + this.message); }, beforeDestroy: function () { console.group('beforeDestroy 销毁前状态===============》'); console.log("%c%s", "color:red","el : " + this.$el); console.log(this.$el); console.log("%c%s", "color:red","data : " + this.$data); console.log("%c%s", "color:red","message: " + this.message); }, destroyed: function () { console.group('destroyed 销毁完成状态===============》'); console.log("%c%s", "color:red","el : " + this.$el); console.log(this.$el); console.log("%c%s", "color:red","data : " + this.$data); console.log("%c%s", "color:red","message: " + this.message) } }) </script> </html> |
控制台输出如下图:
由上图得知:
* 1.beforeCrete: 此时,$el和data都为undefined,没有初始化
* 2.created: 创建后data初始化了,而$el没有
* 3.brforeMount: 挂在之前,$el和data都初始化了,但是message的还没有同步到页面的{{message}}里
* 4.mounted: Vue实例挂载完成了,{{message}}成功变成 “Vue的生命周期”
beforeCreate:创建之前的状态
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el : undefined data : undefined message: undefined |
created:创建完毕的状态
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el : undefined data : [object Object] message: hi |
beforeMount:挂载前的状态
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el : [object HTMLDivElement] <div id="app"><p>{{ message }}</p></div> data : [object Object] message: Vue的生命周期 |
mounted:挂载完毕的状态
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el : [object HTMLDivElement] <div id="app"><p>hi</p></div> data : [object Object] message: Vue的生命周期 |
数据更新(update)
在控制台里输入vm.message = ‘数据更新了’
*当一个数据发生改变时，你的视图也将随之改变，整个更新的过程是：数据改变——导致虚拟DOM的改变——调用这两个生命钩子去改变视图
*这个数据只有和模版中的数据绑定了才会发生更新
beforeDestory和destoryed
*在beferoDestory生命钩子调用之前，所有实例都可以用
*但是当调用后，Vue 实例指示的所有东西都会解绑定，所有的事件监听器会被移除，所有的子实例也会被销毁。
推荐一篇对vue生命周期诠释的比较好的文章:vue 生命周期深入
