vue生命周期和钩子函数

阐述

钩子就好像是把人的出生到死亡分成一个个阶段，你肯定是在出生阶段起名字，而不会在成年或者死亡的阶段去起名字。

或者说你想在出生阶段去约炮，也是不行的。组件也是一样，每个阶段它的内部构造是不一样的。所以一般特定的钩子做特定的事，比如 ajax 获取数据就可以在 mounted 阶段。

1、vue生命周期简介

2、生命周期探究

对于执行顺序和什么时候执行，看上面图基本有个了解了。下面我们将结合代码去看看钩子函数的执行。

    钩子函数
    
    



    {{ message }}
    
    



var vm = new Vue({
    el: '#app',
    data: {
        message : "Welcome Vue"
    },
    methods:{
        change() {
            this.message = 'Datura is me';
        },
        destroy() {
            vm.$destroy();
        }
    },
    beforeCreate: function () {
        console.group('beforeCreate 创建前状态===============》');
        //undefined
        console.log("%c%s", "color:red","el     : " + this.$el);
        //undefined
        console.log("%c%s", "color:red","data   : " + this.$data); 
        //undefined
        console.log("%c%s", "color:red","message: " + this.message);
    },
    created: function () {
        console.group('created 创建完毕状态===============》');
        //undefined
        console.log("%c%s", "color:red","el     : " + this.$el); 
        //[object Object]  =>  已被初始化
        console.log("%c%s", "color:green","data   : " + this.$data); 
        //Welcome Vue  =>  已被初始化
        console.log("%c%s", "color:green","message: " + this.message); 
    },
    beforeMount: function () {
        console.group('beforeMount 挂载前状态===============》');
        //已被初始化
        console.log("%c%s", "color:green","el     : " + (this.$el)); 
        // 当前挂在的元素
        console.log(this.$el); 
        //已被初始化
        console.log("%c%s", "color:green","data   : " + this.$data); 
        //已被初始化
        console.log("%c%s", "color:green","message: " + this.message); 
    },
    mounted: function () {
        console.group('mounted 挂载结束状态===============》');
        //已被初始化
        console.log("%c%s", "color:green","el     : " + this.$el); 
        console.log(this.$el);
        //已被初始化
        console.log("%c%s", "color:green","data   : " + this.$data); 
        //已被初始化
        console.log("%c%s", "color:green","message: " + this.message); 
    },
    beforeUpdate: function () {
        alert("更新前状态");
        console.group('beforeUpdate 更新前状态===============》'); 
        //这里指的是页面渲染新数据之前
        console.log("%c%s", "color:green","el     : " + this.$el);
        console.log(this.$el);
        console.log("%c%s", "color:green","data   : " + this.$data);
        console.log("%c%s", "color:green","message: " + this.message);
        alert("更新前状态2");
    },
    updated: function () {
        console.group('updated 更新完成状态===============》');
        console.log("%c%s", "color:green","el     : " + this.$el);
        console.log(this.$el);
        console.log("%c%s", "color:green","data   : " + this.$data);
        console.log("%c%s", "color:green","message: " + this.message);
    },
    beforeDestroy: function () {
        console.group('beforeDestroy 销毁前状态===============》');
        console.log("%c%s", "color:red","el     : " + this.$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)
    }
})

3、生命周期总结

beforecreate : 举个栗子：可以在这加个loading事件 created ：在这结束loading，还做一些初始化，实现函数自执行 mounted ： 在这发起后端请求，拿回数据，配合路由钩子做一些事情 beforeDestory： 你确认删除XX吗？ destoryed ：当前组件已被删除，清空相关内容