Vue 2.0 浅谈--生命周期和钩子函数
cvhb6863
7年前
<h2>前言</h2> <pre> <code class="language-javascript">用Vue也有一段时间了,发现生命周期是很重要的一部分,稍微懂得了一些东西,特地来分享一下.</code></pre> <h2>生命周期和钩子函数-介绍</h2> <p>啥也不说先上图</p> <p>图-1为 Vue 1.0 生命周期图,图-2为 Vue 2.0 生命周期图,图-3为Vue 1.0 和 Vue 2.0 钩子函数比较</p> <p>重点看 Vue 2.0</p> <p><img src="https://simg.open-open.com/show/14708119166a1b5a018b56f7ff13a357.png"></p> <p><img src="https://simg.open-open.com/show/c690c78b2d70eb617b97a0424dfddda8.png"></p> <p><img src="https://simg.open-open.com/show/8d826e1921b19a9328ae8529883624fd.png"></p> <h2>生命周期和钩子函数-具体</h2> <p>上代码</p> <p>自己粘走执行</p> <pre> <code class="language-javascript"><!DOCTYPE html> <html> <head> <title></title> <script type="text/javascript" src="https://cdn.jsdelivr.net/vue/2.1.3/vue.js"></script> </head> <body> <div id="app"> <p>{{ message }}</p> </div> <script type="text/javascript"> var app = new Vue({ el: '#app', data: { message : "xuxiao is boy" }, 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> </body> </html></code></pre> <p>打开F12可以查看生命周期各个时期的钩子函数的状态,如下图</p> <p><img src="https://simg.open-open.com/show/55382149148c09388653494071be6d3a.png"></p> <p>由上图知:</p> <p>1.beforeCrete: 此时,$el和data都为undefined,没有初始化</p> <p>2.created: 创建后data初始化了,而$el没有</p> <p>3.brforeMount: 挂在之前,$el和data都初始化了</p> <p>4.mounted: Vue实例挂载完成了</p> <p>注意: beforeMount红色矩形框里是{{message}},mounted的红矩形框里是xuxiao is boy,说明挂载前$el的值为'虚拟'的元素节点,挂载后'虚拟'的Dom节点被真实的Dom节点替换</p> <h2>数据更新(update)</h2> <p>在控制台里输入app.message = '数据更新'后</p> <p>如下图</p> <p><img src="https://simg.open-open.com/show/51b44321b31d35b1302803980e27fa96.png"></p> <p>由此可见,当data数据变化时只会触发update</p> <h2>Vue实例解耦(destroy)</h2> <p>在控制台里输入app.$destroy();</p> <p>如下图</p> <p><img src="https://simg.open-open.com/show/05ff3300bedd517adff04850b638a428.png"></p> <p>由图知:</p> <p>执行完destroy操作后,data里的数据没有变化,但是Dom结构还存在,也就是Vue实例不再受控制了,完成了解耦</p> <h2>生命周期和钩子函数-总结</h2> <p>如下图</p> <p>这是把官方 Vue 2.0 生命周期的图例简化后的</p> <p><img src="https://simg.open-open.com/show/b91b53de6efa3c0bc6d9297dc7f66bb3.png"></p> <h3>生命周期钩子函数使用</h3> <p>beforecreate : 举个栗子：可以在这加个loading事件</p> <p>created ：在这结束loading，还做一些初始化，实现函数自执行</p> <p>mounted ： 在这发起后端请求，拿回数据，配合路由钩子做一些事情</p> <p>beforeDestory： 你确认删除XX吗？ destoryed ：当前组件已被删除，清空相关内容</p> <p> </p> <p>来自：https://segmentfault.com/a/1190000009677699</p> <p> </p>