一、vue生命周期图解
下图展示了实例的生命周期。你不需要立马弄明白所有的东西，不过随着你的不断学习和使用，它的参考价值会越来越高。
二、vue钩子函数使用
2.1beforeCreate
在实例初始化之后，数据观测 (data observer) 和 event/watcher 事件配置之前被调用。
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<script src="../statics/vue.min.js"></script> </head>
<body> <div id="app">
{{ message }}
</div> <script> new Vue({
el: "#app",
data: {
message: "Hello Vue",
},
methods: {
myInit: function () {
console.log(this.message);
}
},
beforeCreate(){
console.group('beforeCreate: ');
console.log('el: ', this.$el);
console.log('data: ', this.$data);
console.log('myInit: ', this.myInit);
console.log('message: ', this.message);
}
})
</script>
</body>
</html>
2.2created
在实例创建完成后被立即调用。在这一步，实例已完成以下的配置：数据观测 (data observer)，属性和方法的运算，watch/event 事件回调。然而，挂载阶段还没开始，$el 属性目前不可见。
!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<script src="../statics/vue.min.js"></script> </head>
<body> <div id="app">
{{ message }}
</div> <script> new Vue({
el: "#app",
data: {
message: "Hello Vue",
},
methods: {
myInit: function () {
console.log(this.message);
}
},
beforeCreate(){
console.group('beforeCreate: ');
console.log('el: ', this.$el);
console.log('data: ', this.$data);
console.log('myInit: ', this.myInit);
console.log('message: ', this.message);
},
created(){
console.group('created: ');
console.log('el: ', this.$el);
console.log('data: ', this.$data);
console.log('myInit: ', this.myInit);
console.log('message: ', this.message);
}
})
</script>
</body>
</html>
2.3beforeMount
在挂载开始之前被调用：相关的 render 函数首次被调用。
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<script src="../statics/vue.min.js"></script> </head>
<body> <div id="app">
{{ message }}
</div> <script> new Vue({
el: "#app",
data: {
message: "Hello Vue",
},
methods: {
myInit: function () {
console.log(this.message);
}
},
beforeCreate(){
console.group('beforeCreate: ');
console.log('el: ', this.$el);
console.log('data: ', this.$data);
console.log('myInit: ', this.myInit);
console.log('message: ', this.message);
},
created(){
console.group('created: ');
console.log('el: ', this.$el);
console.log('data: ', this.$data);
console.log('myInit: ', this.myInit);
console.log('message: ', this.message);
},
beforeMount(){
console.group('beforeMount: ');
console.log('el: ', this.$el);
console.log('data: ', this.$data);
console.log('myInit: ', this.myInit);
console.log('message: ', this.message);
}
})
</script>
</body>
</html>
2.4mounted
el 被新创建的 vm.$el 替换，并挂载到实例上去之后调用该钩子。如果 root 实例挂载了一个文档内元素，当 mounted 被调用时 vm.$el 也在文档内。
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<script src="../statics/vue.min.js"></script> </head>
<body> <div id="app">
{{ message }}
</div> <script> new Vue({
el: "#app",
data: {
message: "Hello Vue",
},
methods: {
myInit: function () {
console.log(this.message);
}
},
beforeCreate(){
console.group('beforeCreate: ');
console.log('el: ', this.$el);
console.log('data: ', this.$data);
console.log('myInit: ', this.myInit);
console.log('message: ', this.message);
},
created(){
console.group('created: ');
console.log('el: ', this.$el);
console.log('data: ', this.$data);
console.log('myInit: ', this.myInit);
console.log('message: ', this.message);
},
beforeMount(){
console.group('beforeMount: ');
console.log('el: ', this.$el);
console.log('data: ', this.$data);
console.log('myInit: ', this.myInit);
console.log('message: ', this.message);
},
mounted(){
console.group('mounted: ');
console.log('el: ', this.$el);
console.log('data: ', this.$data);
console.log('myInit: ', this.myInit);
console.log('message: ', this.message);
}
})
</script>
</body>
</html>
2.5beforeUpdate
数据更新时调用，发生在虚拟 DOM 打补丁之前。这里适合在更新之前访问现有的 DOM，比如手动移除已添加的事件监听器。
!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<script src="../statics/vue.min.js"></script> </head>
<body> <div id="app">
{{ message }}
<button @click="myClick">点击修改欢迎语</button>
</div> <script> new Vue({
el: "#app",
data: {
message: "Hello Vue",
},
methods: {
myInit: function () {
console.log(this.message);
},
myClick: function () {
this.message = "Hello World";
}
},
beforeCreate(){
console.group('beforeCreate: ');
console.log('el: ', this.$el);
console.log('data: ', this.$data);
console.log('myInit: ', this.myInit);
console.log('message: ', this.message);
},
created(){
console.group('created: ');
console.log('el: ', this.$el);
console.log('data: ', this.$data);
console.log('myInit: ', this.myInit);
console.log('message: ', this.message);
},
beforeMount(){
console.group('beforeMount: ');
console.log('el: ', this.$el);
console.log('data: ', this.$data);
console.log('myInit: ', this.myInit);
console.log('message: ', this.message);
},
mounted(){
console.group('mounted: ');
console.log('el: ', this.$el);
console.log('data: ', this.$data);
console.log('myInit: ', this.myInit);
console.log('message: ', this.message);
},
beforeUpdate(){
console.group('beforeUpdate: ');
console.log('el: ', this.$el);
console.log('data: ', this.$data);
console.log('myInit: ', this.myInit);
console.log('message: ', this.message);
console.log("beforeData: ", document.getElementById("app").innerHTML);
}
})
</script>
</body>
</html>
该钩子在服务器端渲染期间不被调用，因为只有初次渲染会在服务端进行
2.6updated
由于数据更改导致的虚拟 DOM 重新渲染和打补丁，在这之后会调用该钩子。
当这个钩子被调用时，组件 DOM 已经更新，所以你现在可以执行依赖于 DOM 的操作。然而在大多数情况下，你应该避免在此期间更改状态。如果要相应状态改变，通常最好使用计算属性或 watcher 取而代之。
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<script src="../statics/vue.min.js"></script> </head>
<body> <div id="app">
{{ message }}
<button @click="myClick">点击修改欢迎语</button>
</div> <script> new Vue({
el: "#app",
data: {
message: "Hello Vue",
},
methods: {
myInit: function () {
console.log(this.message);
},
myClick: function () {
this.message = "Hello World";
}
},
beforeCreate(){
console.group('beforeCreate: ');
console.log('el: ', this.$el);
console.log('data: ', this.$data);
console.log('myInit: ', this.myInit);
console.log('message: ', this.message);
},
created(){
console.group('created: ');
console.log('el: ', this.$el);
console.log('data: ', this.$data);
console.log('myInit: ', this.myInit);
console.log('message: ', this.message);
},
beforeMount(){
console.group('beforeMount: ');
console.log('el: ', this.$el);
console.log('data: ', this.$data);
console.log('myInit: ', this.myInit);
console.log('message: ', this.message);
},
mounted(){
console.group('mounted: ');
console.log('el: ', this.$el);
console.log('data: ', this.$data);
console.log('myInit: ', this.myInit);
console.log('message: ', this.message);
},
beforeUpdate(){
console.group('beforeUpdate: ');
console.log('el: ', this.$el);
console.log('data: ', this.$data);
console.log('myInit: ', this.myInit);
console.log('message: ', this.message);
console.log("beforeData: ", document.getElementById("app").innerHTML);
},
updated(){
console.group('updated: ');
console.log('el: ', this.$el);
console.log('data: ', this.$data);
console.log('myInit: ', this.myInit);
console.log('message: ', this.message);
console.log("updated: ", document.getElementById("app").innerHTML);
}
})
</script>
</body>
</html>
2.7activated
keep-alive 组件激活时调用。<keep-alive> 包裹动态组件时，会缓存不活动的组件实例，而不是销毁它们
该钩子在服务器端渲染期间不被调用。
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<script src="../statics/vue.min.js"></script> </head>
<body> <div id="app"> </div> <script> let MyLifeCycle = {
template: `
<div>
<span>这是beforeDestroy</span>
</div>
`,
created(){
console.log("created");
},
activated(){
console.log("activated");
},
deactivated(){
console.log("deactivated");
},
beforeDestroy(){
console.log("beforeDestroy");
},
destroyed(){
console.log("destroyed");
}
}; let App = {
template: `
<div>
<keep-alive>
<my-lifecycle v-if="isShow"></my-lifecycle>
</keep-alive>
<button @click="myClick">点击创建消除beforeDestroy</button>
</div>
`,
components: {
'my-lifecycle': MyLifeCycle
},
data(){
return {
isShow: true,
}
},
methods: {
myClick: function () {
this.isShow = !this.isShow;
}
}
}; new Vue({
el: "#app",
template: `<App></App>`,
data: {
message: "Hello Vue",
},
methods: {
myInit: function () {
console.log(this.message);
},
myClick: function () {
this.message = "Hello World";
}
},
components: {
App
}
})
</script>
</body>
</html>
2.8deactivated
keep-alive 组件停用时调用。
该钩子在服务器端渲染期间不被调用。
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<script src="../statics/vue.min.js"></script> </head>
<body> <div id="app"> </div> <script> let MyLifeCycle = {
template: `
<div>
<span>这是beforeDestroy</span>
</div>
`,
created(){
console.log("created");
},
activated(){
console.log("activated");
},
deactivated(){
console.log("deactivated");
},
beforeDestroy(){
console.log("beforeDestroy");
},
destroyed(){
console.log("destroyed");
}
}; let App = {
template: `
<div>
<keep-alive>
<my-lifecycle v-if="isShow"></my-lifecycle>
</keep-alive>
<button @click="myClick">点击创建消除beforeDestroy</button>
</div>
`,
components: {
'my-lifecycle': MyLifeCycle
},
data(){
return {
isShow: true,
}
},
methods: {
myClick: function () {
this.isShow = !this.isShow;
}
}
}; new Vue({
el: "#app",
template: `<App></App>`,
data: {
message: "Hello Vue",
},
methods: {
myInit: function () {
console.log(this.message);
},
myClick: function () {
this.message = "Hello World";
}
},
components: {
App
}
})
</script>
</body>
</html>
2.10destroyed
Vue 实例销毁后调用。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。
该钩子在服务器端渲染期间不被调用。
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<script src="../statics/vue.min.js"></script> </head>
<body> <div id="app"> </div> <script> let MyLifeCycle = {
template: `
<div>
<span>这是beforeDestroy</span>
</div>
`,
created(){
console.log("created");
},
beforeDestroy(){
console.log("beforeDestroy");
},
destroyed(){
console.log("destroyed");
}
}; let App = {
template: `
<div>
<my-lifecycle v-if="isShow"></my-lifecycle>
<button @click="myClick">点击创建消除beforeDestroy</button>
</div>
`,
components: {
'my-lifecycle': MyLifeCycle
},
data(){
return {
isShow: true,
}
},
methods: {
myClick: function () {
this.isShow = !this.isShow;
}
}
}; new Vue({
el: "#app",
template: `<App></App>`,
data: {
message: "Hello Vue",
},
methods: {
myInit: function () {
console.log(this.message);
},
myClick: function () {
this.message = "Hello World";
}
},
components: {
App
}
})
</script>
</body>
</html>