饮水思源：
https://vuejs.org/v2/guide/instance.html#Instance-Lifecycle-Hooks
https://www.bilibili.com/video/BV1Zy4y1K7SH?p=49&spm_id_from=pageDriver
引入生命周期——一个渐变特效
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8" />
<title></title>
<script src="JS/vue.js"></script>
</head>
<body>
<h1>一个渐变特效&VUE的生命周期</h1>
<div id="root">
<h2 :style="{opacity}">一个渐变的文字</h2>
</div>
<script>
new Vue({
el: "#root",
data: {
opacity: 0.5
},
mounted() {
console.log("mount是挂载的意思，mounted是挂载完毕，也就是dom被放入页面后");
setInterval(() => {
this.opacity -= 0.01;
if (this.opacity <= 0) this.opacity = 1;
}, 20)
},
});
</script>
</body>
</html>
两个重要的钩子——mounted和beforeDestroy
单纯stop，组件确实不再更新，但是计时器没有关掉，也就是“setInterval没被干掉”还会不断输出：
<script>
new Vue({
el: "#root",
data: {
opacity: 0.5,
},
methods: {
stop() {
this.$destroy();
}
},
mounted() {
this.tid = setInterval(() => {
console.log("setInterval没被干掉")
this.opacity -= 0.01;
if (this.opacity <= 0) this.opacity = 1;
}, 20)
},
});
</script>
正确的写法，在销毁之前还需要处理后事，并且这个逻辑应该写在自己身上：
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8" />
<title></title>
<script src="JS/vue.js"></script>
</head>
<body>
<h1>一个渐变特效&VUE的生命周期</h1>
<div id="root">
<h2 :style="{opacity}">一个渐变的文字</h2>
<button v-on:click="stop">点我停止渐变</button>
</div>
<script>
new Vue({
el: "#root",
data: {
opacity: 0.5,
},
methods: {
stop() {
this.$destroy();
}
},
mounted() {
this.tid = setInterval(() => {
console.log("setInterval没被干掉")
this.opacity -= 0.01;
if (this.opacity <= 0) this.opacity = 1;
}, 20)
},
beforeDestroy() {
clearInterval(this.tid)
},
});
</script>
</body>
</html>