VUE 添加事件、渲染、组件 - 前端入门

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VUE 元素添加事件

v-on: 事件指令 , 简写: @
event, 在 vue3: $evnet
事件修饰符: 对当前的事件行为进行干预
@click.prevent: 阻止默认行为
@click.prevent.stop

<!DOCTYPE html>
<html lang="zh-CN">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>事件绑定</title>
    <script src="https://unpkg.com/vue@next"></script>
  </head>
  <body>
    <!-- vue3 -->
    <div class="app">
      <p>
        <!-- v-on: 事件指令 , @ -->
        <!-- event, 在vue3: $evnet  -->
        <a href="helo10086.cn" v-on:click="showUrl($event)">vue1: 显示网址: </a>
        <span class="url">{{url}}</span>
      </p>
      <!-- 事件修饰符: 对当前的事件行为进行干预 -->
      <p>
        <!-- v-on: 事件指令 , @ -->
        <!-- event, 在vue3: $evnet  -->
        <!-- @click.prevent: 阻止默认行为  -->
        <a href="helo10086.cn" @click.prevent="this.url = $event.target.href"
          >vue2: 显示网址:
        </a>
        <span class="url">{{url}}</span>
      </p>
      <!-- 在父级上的同名事件,因为事件冒泡机制而被自动的调用了 -->
      <p onclick="alert('hello help!')">
        <!-- @click.stop: 阻止冒泡 -->
        <a
          href="helo10086.cn"
          @click.prevent.stop="this.url = $event.target.href"
          >vue3: 显示网址:
        </a>
        <span class="url">{{url}}</span>
      </p>
    </div>
    <script>
      const app = Vue.createApp({
        data() {
          return {
            url: null,
          };
        },
        methods: {
          showUrl(ev) {
            // 防止默认行为
            ev.preventDefault();
            console.log(ev === event);
            // this -> vue实例
            console.log(this);
            console.log(ev.target);
            this.url = ev.target.href;
          },
        },
      }).mount(".app");
    </script>
  </body>
</html>

[http://help10086.cn/0114/demo1.html]

VUE 条件渲染与列表渲染

v-for , 对应原生的 for - of

<!-- 列表渲染 -->
<!DOCTYPE html>
<html lang="zh-CN">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>列表渲染</title>
    <script src="https://unpkg.com/vue@next"></script>
  </head>
  <body>
    <div class="app">
      <!-- array: v-for , 对应原生的 for - of  -->
      <ul>
        <!-- 提高效率,一定要加 :key 为了借助diff算法,key必须选择一个永远唯一的值 -->
        <li v-for="(city,index) of cities" :key="index">{{index}}->{{city}}</li>
      </ul>
      <!-- obj: v-for  -->
      <ul>
        <!-- prop -> property 属性 -->
        <li v-for="(item,prop,index) of user" :key="index">
          {{index}} ->{{prop}} => {{item}}
        </li>
      </ul>
      <!-- ArrayObj: v-for  -->
      <ul>
        <li v-for="(user,index) of users" :key="index">
          {{user.name}}: ({{user.email}})
        </li>
      </ul>
    </div>
    <script>
      const app = Vue.createApp({
        data() {
          return {
            // array
            cities: ["tayninh", "nhontrach", "longthanh"],
            // object
            user: {
              name: "help",
              email: "help@foxmail.com",
            },
            // array of object
            users: [
              {
                name: "lan",
                email: "lan@foxmail.com",
              },
              {
                name: "hoang",
                email: "hoang@foxmail.com",
              },
              {
                name: "hope",
                email: "hope@foxmail.com",
              },
            ],
          };
        },
      }).mount(".app");
    </script>
  </body>
</html>
<!-- 条件渲染 -->
<!DOCTYPE html>
<html lang="zh-CN">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>条件渲染</title>
    <script src="https://unpkg.com/vue@next"></script>
  </head>
  <body>
    <div class="app">
      <!-- if  -->
      <p v-if="flag">{{message}}</p>
      <button @click="flag=!flag" v-text="flag ? '隐藏' : '显示'"></button>
      <!-- if -- if else -- if else -- else  -->
      <p v-if="salary > 0 && salary < 2000">{{grade[1]}}</p>
      <p v-else-if="salary >= 2000 && salary < 6000">{{grade[2]}}</p>
      <p v-else-if="salary >= 6000 && salary < 10000">{{grade[3]}}</p>
      <p v-else-if="salary >= 10000 && salary < 15000">{{grade[4]}}</p>
      <p v-else-if="salary >= 15000">{{grade[5]}}</p>
      <p v-else>{{grade[0]}}</p>
    </div>
    <script>
      const app = Vue.createApp({
        data() {
          return {
            message: "20220116, 准备领完年终奖，回家过年吧!",
            flag: false,
            // 会员级别
            grade: [
              "操作工",
              "业务员",
              "主管",
              "一般管理",
              "中层管理",
              "高层管理",
            ],
            // 积分
            salary: 100000,
          };
        },
      }).mount(".app");
    </script>
  </body>
</html>

列表渲染：[http://help10086.cn/0114/demo2.html]
条件渲染：[http://help10086.cn/0114/demo3.html]

VUE 计算属性与侦听器

例生命周期, mounted: 当 vue 实例加载完成的时候会自动调用(onload)

<!DOCTYPE html>
<html lang="zh-CN">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <script src="https://unpkg.com/vue@next"></script>
    <title>计算属性,侦听器属性</title>
    <style>
      table {
        width: 26em;
        text-align: center;
        border-collapse: collapse;
      }
      table caption {
        font-size: 1.5em;
        margin-bottom: 0.6em;
      }
      thead {
        background-color: lightcyan;
      }
      th,
      td {
        border: 1px solid #000;
        height: 2em;
      }
    </style>
  </head>
  <body>
    <div class="app">
      <table>
        <caption>
          购物车
        </caption>
        <thead>
          <tr>
            <th>ID</th>
            <th>品名</th>
            <th>单价</th>
            <th>数量</th>
            <th>金额</th>
          </tr>
        </thead>
        <tbody>
          <tr>
            <td>20220116</td>
            <td>iphone 13</td>
            <td>{{price}}</td>
            <td><input type="number" v-model="num" style="width: 4em" /></td>
            <!-- <td>{{price * num}}</td> -->
            <td>{{payAmount}}</td>
          </tr>
        </tbody>
      </table>
      <!-- 侦听器来监听金额的变化,设置优惠价格:用户实际支付的钱 -->
      <!-- <p>实付金额: {{disAmount}}, 优惠了 : <span style="color: red">{{payAmount-disAmount}}</span></p> -->
      <p>
        实付金额: {{disAmount}}, 优惠了 :
        <span style="color: #ff0000">{{difAmount}}</span>
      </p>
    </div>
    <script>
      const app = Vue.createApp({
        data() {
          return {
            price: 10000,
            num: 0,
          };
        },
        // 计算属性: 访问器属性
        computed: {
          payAmount: {
            get() {
              return this.price * this.num;
            },
            set(value) {
              // 这个通常用来做测试
            },
          },
        },
        // 侦听器属性
        watch: {
          // current: 新值/当前值, origin: 原值/旧值
          payAmount(current, origin) {
            console.log(current, origin);
            switch (true) {
              case current > 10000 && current < 20000:
                this.disAmount = this.payAmount * 0.99;
                break;
              case current >= 20000 && current < 30000:
                this.disAmount = this.payAmount * 0.98;
                break;
              case current >= 30000 && current < 40000:
                this.disAmount = this.payAmount * 0.97;
              case current >= 40000 && current < 50000:
                this.disAmount = this.payAmount * 0.96;
                break;
              case current > 50000:
                this.disAmount = this.payAmount * 0.95;
                break;
              default:
                this.disAmount = this.payAmount;
            }
            this.difAmount = this.payAmount - this.disAmount;
          },
        },
        // 实例生命周期, mounted: 当vue实例加载完成的时候会自动调用(onload)
        mounted() {
          this.num = 1;
        },
      }).mount(".app");
    </script>
  </body>
</html>

[http://help10086.cn/0114/demo5.html]

VUE 组件与组件之间的通信

组件,vue 指令本质是自定义属性
vue 组件本质就是自定义标签
子组件传参:自定义属性
监听子组件: $emit(自定义事件, 向父组件传递的参数[可选])

<!-- VUE组件 -->
<!DOCTYPE html>
<html lang="zh-CN">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>组件:全局组件</title>
    <script src="https://unpkg.com/vue@next"></script>
  </head>
  <body>
    <div class="app">
      <!-- vue指令 -> 自定义属性 -->
      <div v-text="'hello'"></div>
      <!-- vue组件 -> 自定义标签 -->
      <button-counter></button-counter>
    </div>
    <template id="counter">
      <button @click="count++">点赞: {{count}}</button>
    </template>
    <script>
      // 1. 创建实例
      const app = Vue.createApp({});
      // 2. 注册组件
      app.component("ButtonCounter", {
        template: "#counter",
        data() {
          return {
            count: 0,
          };
        },
      });
      // 3. 绑定挂载点
      app.mount(".app");
    </script>
  </body>
</html>
<!-- 子组件传参 -->
<!DOCTYPE html>
<html lang="zh-CN">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>子组件传参</title>
    <script src="https://unpkg.com/vue@next"></script>
  </head>
  <body>
    <div class="app">
      <button-counter username="admin" email="admin@qq.com"></button-counter>
    </div>
    <template id="counter">
      <button @click="count++">点赞: {{count}}</button>
      <p>用户: {{username}}</p>
      <p>邮箱: {{email}}</p>
    </template>
    <script>
      // 1. 创建实例
      const app = Vue.createApp({});
      // 2. 注册组件
      app.component("ButtonCounter", {
        // 自定义属性
        props: ["username", "email"],
        template: "#counter",
        data() {
          return {
            count: 0,
          };
        },
      });
      // 3. 绑定挂载点
      app.mount(".app");
    </script>
  </body>
</html>
<!-- 监听子组件事件 -->
<!DOCTYPE html>
<html lang="zh-CN">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>监听子组件事件</title>
    <script src="https://unpkg.com/vue@next"></script>
  </head>
  <body>
    <div class="app">
      <button-counter
        username="help"
        email="help10086@foxmail.com"
        @review-count="review"
      ></button-counter>
    </div>
    <template id="counter">
      <button @click="count++">点赞: {{count}}</button>
      <p>用户: {{username}}</p>
      <p>邮箱: {{email}}</p>
      <!-- 发布订阅 -->
      <!-- $emit(自定义事件, 向父组件传递的参数[可选]) -->
      <button @click="$emit('reviewCount', this.count)">评价</button>
    </template>
    <script>
      // 1. 创建实例
      const app = Vue.createApp({
        methods: {
          review(count) {
            console.log(count);
            if (count >= 20) {
              alert("感谢家人的支持!");
            }
          },
        },
      });
      // 2. 注册组件
      app.component("ButtonCounter", {
        props: ["username", "email"],
        template: "#counter",
        data() {
          return {
            count: 0,
          };
        },
      });
      // 3. 绑定挂载点
      app.mount(".app");
      // 1. 向子组传传参: props:  [....]
      // 2. 子组件向父组通信:
      //    2.1 子组件: $emit(customEvent, ...args)
      //    2.2 父组件: @customEvent(...args)
    </script>
  </body>
</html>

[http://help10086.cn/0114/demo7.html]
[http://help10086.cn/0114/demo8.html]

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