004.Vue3入门，使用绑定属性时undefined和disabled用法

1、代码如下：

<template>
  <div v-bind:id="myId1" v-bind:class="testCls">测试1</div>
  <div v-bind:id="myId2" v-bind:title="testTitle">测试2</div>
  <div :id="myId3" :class="testCls">测试2</div>
  <button :disabled="isButtonDisabled">按钮</button>
</template>

<script>
export default {
  data() {
    return {
      testCls: "appclass",
      myId1: "appId1",
      myId2: "appId2",
      myId3: "appId3",
      title: undefined,
      isButtonDisabled: true
    }
  }
}
</script>

<style>
.appclass {
  color: red;
  font-size: 30px;
}

</style>

2、效果如下：