Vue生命周期
有时候，我们需要在实例创建过程中进行一些初始化的工作，以帮助我们完成项目中更复杂更丰富的需求开发，针对这样的需求，Vue提供给我们一系列的钩子函数。
本文详细介绍了Vue实例在创建和销毁的过程中，我们可以利用的钩子函数。
下面，我们结合官方文档提供的Vue实例生命周期图，来进行钩子函数的解析。
一、beforeCreate
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.js"></script>
</head>
<body>
<div id="app">
{{ name }}
<button @click="myClick">点击修改数据</button>
</div>
<script>
new Vue({
el: "#app",
// 在template中使用组件与在body中使用组件是一样的
// template: `<cont></cont>`,
data: {
name: "Alex"
},
methods: {
myClick: function () {
this.name = "Pizza";
}
},
beforeCreate() {
console.group("beforeCreate");
console.log("el: ", this.$el);
console.log("data: ", this.$data);
console.log("name: ", this.name);
console.log("myClick: ", this.myClick);
console.log("innerHTML: ", document.getElementById("app").innerHTML);
},
});
</script>
</body>
</html>
二、created
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，$el 属性目前不可见。
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<script src="../statics/vue.js"></script>
</head>
<body>
<div id="app">
{{ name }}
<button @click="myClick">点击修改数据</button>
</div>
<script>
new Vue({
el: "#app",
// 在template中使用组件与在body中使用组件是一样的
// template: `<cont></cont>`,
data: {
name: "Alex"
},
methods: {
myClick: function () {
this.name = "Pizza";
}
},
beforeCreate() {
console.group("beforeCreate");
console.log("el: ", this.$el);
console.log("data: ", this.$data);
console.log("name: ", this.name);
console.log("myClick: ", this.myClick);
console.log("innerHTML: ", document.getElementById("app").innerHTML);
},
created() {
console.group("Created");
console.log("el: ", this.$el);
console.log("data: ", this.$data);
console.log("name: ", this.name);
console.log("myClick: ", this.myClick);
console.log("innerHTML: ", document.getElementById("app").innerHTML);
}
})
</script>
</body>
</html>
三、beforeMount
在挂载开始之前被调用：相关的 render 函数首次被调用。
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<script src="../statics/vue.js"></script>
</head>
<body>
<div id="app">
{{ name }}
<button @click="myClick">点击修改数据</button>
</div>
<script>
new Vue({
el: "#app",
// 在template中使用组件与在body中使用组件是一样的
// template: `<cont></cont>`,
data: {
name: "Alex"
},
methods: {
myClick: function () {
this.name = "Pizza";
}
},
beforeCreate() {
console.group("beforeCreate");
console.log("el: ", this.$el);
console.log("data: ", this.$data);
console.log("name: ", this.name);
console.log("myClick: ", this.myClick);
console.log("innerHTML: ", document.getElementById("app").innerHTML);
},
created() {
console.group("Created");
console.log("el: ", this.$el);
console.log("data: ", this.$data);
console.log("name: ", this.name);
console.log("myClick: ", this.myClick);
console.log("innerHTML: ", document.getElementById("app").innerHTML);
},
beforeMount() {
console.group("beforeMount");
console.log("el: ", this.$el);
console.log("data: ", this.$data);
console.log("name: ", this.name);
console.log("myClick: ", this.myClick);
console.log("innerHTML: ", document.getElementById("app").innerHTML);
}
})
</script>
</body>
</html>
四、mounted
el 被新创建的 vm.$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.$el 也在文档内。
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<script src="../statics/vue.js"></script>
</head>
<body>
<div id="app">
{{ name }}
<button @click="myClick">点击修改数据</button>
</div>
<script>
new Vue({
el: "#app",
// 在template中使用组件与在body中使用组件是一样的
// template: `<cont></cont>`,
data: {
name: "Alex"
},
methods: {
myClick: function () {
this.name = "Pizza";
}
},
beforeCreate() {
console.group("beforeCreate");
console.log("el: ", this.$el);
console.log("data: ", this.$data);
console.log("name: ", this.name);
console.log("myClick: ", this.myClick);
console.log("innerHTML: ", document.getElementById("app").innerHTML);
},
created() {
console.group("Created");
console.log("el: ", this.$el);
console.log("data: ", this.$data);
console.log("name: ", this.name);
console.log("myClick: ", this.myClick);
console.log("innerHTML: ", document.getElementById("app").innerHTML);
},
beforeMount() {
console.group("beforeMount");
console.log("el: ", this.$el);
console.log("data: ", this.$data);
console.log("name: ", this.name);
console.log("myClick: ", this.myClick);
console.log("innerHTML: ", document.getElementById("app").innerHTML);
},
mounted() {
console.group("mounted");
console.log("el: ", this.$el);
console.log("data: ", this.$data);
console.log("name: ", this.name);
console.log("myClick: ", this.myClick);
console.log("innerHTML: ", document.getElementById("app").innerHTML);
},
})
</script>
</body>
</html>
五、beforeUpdate
数据更新时调用，发生在虚拟 DOM 打补丁之前。这里适合在更新之前访问现有的 DOM，比如手动移除已添加的事件监听器。
该钩子在服务器端渲染期间不被调用，因为只有初次渲染会在服务端进行
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<script src="../statics/vue.js"></script>
</head>
<body>
<div id="app">
{{ name }}
<button @click="myClick">点击修改数据</button>
</div>
<script>
new Vue({
el: "#app",
// 在template中使用组件与在body中使用组件是一样的
// template: `<cont></cont>`,
data: {
name: "Alex"
},
methods: {
myClick: function () {
this.name = "Pizza";
}
},
beforeCreate() {
console.group("beforeCreate");
console.log("el: ", this.$el);
console.log("data: ", this.$data);
console.log("name: ", this.name);
console.log("myClick: ", this.myClick);
console.log("innerHTML: ", document.getElementById("app").innerHTML);
},
created() {
console.group("Created");
console.log("el: ", this.$el);
console.log("data: ", this.$data);
console.log("name: ", this.name);
console.log("myClick: ", this.myClick);
console.log("innerHTML: ", document.getElementById("app").innerHTML);
},
beforeMount() {
console.group("beforeMount");
console.log("el: ", this.$el);
console.log("data: ", this.$data);
console.log("name: ", this.name);
console.log("myClick: ", this.myClick);
console.log("innerHTML: ", document.getElementById("app").innerHTML);
},
mounted() {
console.group("mounted");
console.log("el: ", this.$el);
console.log("data: ", this.$data);
console.log("name: ", this.name);
console.log("myClick: ", this.myClick);
console.log("innerHTML: ", document.getElementById("app").innerHTML);
},
beforeUpdate() {
console.group("beforeUpdate");
console.log("el: ", this.$el);
console.log("data: ", this.$data);
console.log("name: ", this.name);
console.log("myClick: ", this.myClick);
console.log("innerHTML: ", document.getElementById("app").innerHTML);
}
})
</script>
</body>
</html>
六、updated
由于数据更改导致的虚拟 DOM 重新渲染和打补丁，在这之后会调用该钩子。
当这个钩子被调用时，组件 DOM 已经更新，所以你现在可以执行依赖于 DOM 的操作。然而在大多数情况下，你应该避免在此期间更改状态。如果要相应状态改变，通常最好使用计算属性或 watcher取而代之。
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<script src="../statics/vue.js"></script>
</head>
<body>
<div id="app">
{{ name }}
<button @click="myClick">点击修改数据</button>
</div>
<script>
new Vue({
el: "#app",
// 在template中使用组件与在body中使用组件是一样的
// template: `<cont></cont>`,
data: {
name: "Alex"
},
methods: {
myClick: function () {
this.name = "Pizza";
}
},
beforeCreate() {
console.group("beforeCreate");
console.log("el: ", this.$el);
console.log("data: ", this.$data);
console.log("name: ", this.name);
console.log("myClick: ", this.myClick);
console.log("innerHTML: ", document.getElementById("app").innerHTML);
},
created() {
console.group("Created");
console.log("el: ", this.$el);
console.log("data: ", this.$data);
console.log("name: ", this.name);
console.log("myClick: ", this.myClick);
console.log("innerHTML: ", document.getElementById("app").innerHTML);
},
beforeMount() {
console.group("beforeMount");
console.log("el: ", this.$el);
console.log("data: ", this.$data);
console.log("name: ", this.name);
console.log("myClick: ", this.myClick);
console.log("innerHTML: ", document.getElementById("app").innerHTML);
},
mounted() {
console.group("mounted");
console.log("el: ", this.$el);
console.log("data: ", this.$data);
console.log("name: ", this.name);
console.log("myClick: ", this.myClick);
console.log("innerHTML: ", document.getElementById("app").innerHTML);
},
beforeUpdate() {
console.group("beforeUpdate");
console.log("el: ", this.$el);
console.log("data: ", this.$data);
console.log("name: ", this.name);
console.log("myClick: ", this.myClick);
console.log("innerHTML: ", document.getElementById("app").innerHTML);
},
updated() {
console.log("updated");
console.log("el: ", this.$el);
console.log("data: ", this.$data);
console.log("name: ", this.name);
console.log("myClick: ", this.myClick);
console.log("innerHTML: ", document.getElementById("app").innerHTML);
}
})
</script>
</body>
</html>
七、activated
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">
<App></App>
</div>
<script>
let Laside = {
template: `
<div>
<h1>{{ message }}</h1>
<button @click="changeData">点击修改数据</button>
</div>
`,
data () {
return {
message: "Hello Vue!"
}
},
methods: {
changeData: function () {
this.mes = "Pizza is here!";
}
},
// 组件的创建和销毁对性能有影响
beforeDestroy () {
console.log("beforeDestroy");
},
destroyed () {
console.log("destroyed");
},
activated () {
console.log("activated");
},
};
let App = {
template: `
<div >
<keep-alive>
<Laside v-if="isShow"></Laside>
</keep-alive>
<button @click="showHide">创建消除组件</button>
</div>
`,
components: {
"Laside": Laside,
},
methods: {
showHide: function () {
this.isShow = !this.isShow;
}
},
data () {
return {
isShow: true,
}
}
};
new Vue({
el: "#app",
// 在template中使用组件与在body中使用组件是一样的
// template: `<cont></cont>`,
components: {
App,
}
})
</script>
</body>
</html>
七、deactivated
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">
<App></App>
</div>
<script>
let Laside = {
template: `
<div>
<h1>{{ mes }}</h1>
<button @click="changeData">点击修改数据</button>
</div>
`,
data () {
return {
message: "Hello Vue!"
}
},
methods: {
changeData: function () {
this.mes = "Pizza is here!";
}
},
// 组件的创建和销毁对性能有影响
beforeDestroy () {
console.log("beforeDestroy");
},
destroyed () {
console.log("destroyed");
},
activated () {
console.log("activated");
},
deactivated () {
console.log("deactivated");
}
};
let App = {
template: `
<div >
<keep-alive>
<Laside v-if="isShow"></Laside>
</keep-alive>
<button @click="showHide">创建消除组件</button>
</div>
`,
components: {
"Laside": Laside,
},
methods: {
showHide: function () {
this.isShow = !this.isShow;
}
},
data () {
return {
isShow: true,
}
}
};
new Vue({
el: "#app",
// 在template中使用组件与在body中使用组件是一样的
// template: `<cont></cont>`,
components: {
App,
}
})
</script>
</body>
</html>
八、beforeDestroy
实例销毁之前调用。在这一步，实例仍然完全可用。频繁的创建和销毁组件对性能的影响很大，因此可以使用activated和deactivated。
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.js"></script>
</head>
<body>
<div id="app">
<App></App>
</div>
<script>
let Laside = {
template: `
<div>
<h1>{{ mes }}</h1>
<button @click="changeData">点击修改数据</button>
</div>
`,
data () {
return {
mes: "Hello Vue!"
}
},
methods: {
changeData: function () {
this.mes = "Pizza is here!";
}
},
// 组件的创建和销毁对性能有影响
beforeDestroy() {
console.log("beforeDestroy");
},
};
let App = {
template: `
<div >
<Laside v-if="isShow"></Laside>
<button @click="showHide">创建消除组件</button>
</div>
`,
components: {
"Laside": Laside,
},
methods: {
showHide: function () {
this.isShow = !this.isShow;
}
},
data () {
return {
isShow: true,
}
}
};
new Vue({
el: "#app",
// 在template中使用组件与在body中使用组件是一样的
// template: `<cont></cont>`,
components: {
App,
}
})
</script>
</body>
</html>
九、destroyed
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">
<App></App>
</div>
<script>
let Laside = {
template: `
<div>
<h1>{{ mes }}</h1>
<button @click="changeData">点击修改数据</button>
</div>
`,
data () {
return {
mes: "Hello Vue!"
}
},
methods: {
changeData: function () {
this.mes = "Pizza is here!";
}
},
// 组件的创建和销毁对性能有影响
beforeDestroy() {
console.log("beforeDestroy");
},
destroyed () {
console.log("destroyed");
}
};
let App = {
template: `
<div >
<Laside v-if="isShow"></Laside>
<button @click="showHide">创建消除组件</button>
</div>
`,
components: {
"Laside": Laside,
},
methods: {
showHide: function () {
this.isShow = !this.isShow;
}
},
data () {
return {
isShow: true,
}
}
};
new Vue({
el: "#app",
// 在template中使用组件与在body中使用组件是一样的
// template: `<cont></cont>`,
components: {
App,
}
})
</script>
</body>
</html>
好了，关于Vue.js实例的生命周期就介绍到这里。