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                <div id="app">
  <transition @before-enter="handleBeforeClick" @enter="handlEnterClick" @after-enter="handlAfterClick">
    <div v-show="show">
  <button @click="handleBtnClick">toggle</button>




                var app = new Vue({
  el: "#app",
  data: {
    mess: "hello world",
    show: true
  methods: {
    handleBtnClick: function () { = !;
    // 显示/入场 的时候执行,一个参数
    handleBeforeClick: function (el) { = "red";
      console.log("handleBeforeClick", el);
    // 显示/入场 的时候执行,两个参数el,done(回调函数)
    handlEnterClick: function (el, done) {
      setTimeout(() => { = "blue";
        // 要调用一下done回调函数,证明动画已经结束了
      }, 1000);
      setTimeout(() => {
      }, 3000);
      console.log("handlEnterClick", el, done);
    handlAfterClick: function (el) { = "pink";