02Vue的常用特性

作者: 攻城老狮 | 来源:发表于2021-01-31 21:00 被阅读0次

02Vue的常用特性
WKWebView 几个不常用的特性
常用的特性
C++ 11常用特性
字典
Math方法和es新特性
Vue 常用特性
Unity常用特性
Vue常用特性
Vue常用特性

Vue的常用特性

表单操作

表单元素

包含 text,radio,checkbox,select,textarea的Vue操作方式，另外提交禁用默认的表单提交方式，采用手动的ajax提交表单数据

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style type="text/css">
  
  form div {
    height: 40px;
    line-height: 40px;
  }
  form div:nth-child(4) {
    height: auto;
  }
  form div span:first-child {
    display: inline-block;
    width: 100px;
  }
  </style>
</head>
<body>
  <div id="app">
    <form action="http://www.baidu.com">
      <div>
        <span>姓名：</span>
        <span>
          <input type="text" v-model="uname">
        </span>
      </div>
      <div>
        <span>性别：</span>
        <span>
          <input type="radio" id="male" value="1" v-model="gender">
          <label for="male">男</label>
          <input type="radio" id="female" value="2" v-model="gender">
          <label for="female">女</label>
        </span>
      </div>
      <div>
        <span>爱好：</span>
        <input type="checkbox" id="ball" value="1" v-model="hobby">
        <label for="ball">篮球</label>
        <input type="checkbox" id="sing" value="2" v-model="hobby">
        <label for="sing">唱歌</label>
        <input type="checkbox" id="code" value="3" v-model="hobby">
        <label for="code">写代码</label>
      </div>
      <div>
        <span>职业：</span>
        <select v-model="occupation">
          <option value="0">请选择职业...</option>
          <option value="1">教师</option>
          <option value="2">软件工程师</option>
          <option value="3">律师</option>
        </select>
      </div>
      <div>
        <span>个人简介：</span>
        <textarea v-model="desc"></textarea>
      </div>
      <div>
        <input type="submit" value="提交" v-on:click.prevent="handle">
      </div>
    </form>
  </div>
  <script type="text/javascript" src="js/vue.js"></script>
  <script type="text/javascript">
    /*
      表单基本操作
    */
    var vm = new Vue({
      el: '#app',
      data: {
        uname: "yorick",
        gender: 1,
        hobby: [1,2],
        occupation: 2,
        desc: "Hello World"
      },
      methods: {
        handle: function(){
          console.log(this.uname);
          console.log(this.gender);
          console.log(this.hobby.toString());
          console.log(this.occupation);
          console.log(this.desc);
        }
      }
    });
  </script>
</body>
</html>

表单域修饰符

1.number:将字符串转换为数值类型
2.trim:去除内容两侧的空格
3.lazy:将input事件转变为change事件(失去焦点时触发)

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <div id="app">
      <input type="text" v-model.number="age">
      <input type="text" v-model.trim="info">
      <input type="text" v-model.lazy="desc">
      <div v-text="desc"></div>
      <button v-on:click="handle">提交</button>
    </div>
    <script src="js/jquery-3.4.1.js"></script>
    <script src="js/vue.js"></script>
    <script>
       var vm = new Vue({
           el: "#app",
           data: {
               age: "",
               info: "",
               desc: ""
           },
           methods:{
               handle: function(){
                    console.log(this.age + 10); //数值计算，而并非字符串拼接
                    console.log(this.info.length); //忽略空格的长度
               }
           }
       });
    </script>
</body>

</html>

自定义指令

无参数自定义指令定义的语法规则

Vue.directive("focus",{
    inserted: function(el){
        el.focus();
    }
});

无参数自定义指令用法

<input type="text" v-focus>

实例：通过自定义指令实现刷新页面后默认光标选中输入框

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <div id="app">
        <input type="text" v-focus>
    </div>
    <script src="js/jquery-3.4.1.js"></script>
    <script src="js/vue.js"></script>
    <script>
        Vue.directive("focus",{
            inserted: function(el){
                el.focus();
            }
        });
        var vm = new Vue({
           el: "#app",
           data: {

           },
           methods:{

           }
       });
    </script>
</body>

</html>

带参数的自定义指令的语法规则

Vue.directive("color",{
    bind: function(el,binding){
        el.style.backgroundColor = binding.value.color;
    }
});

带参数的自定义指令用法

<input type="text" v-color="msg">

实例：通过带参数的自定义指令实现改变输入框的背景颜色

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <div id="app">
        <input type="text" v-color="msg">
    </div>
    <script src="js/jquery-3.4.1.js"></script>
    <script src="js/vue.js"></script>
    <script>
        Vue.directive("color",{
            bind: function(el,binding){
                el.style.backgroundColor = binding.value.color;
            }
        });
        var vm = new Vue({
           el: "#app",
           data: {
               msg:{
                   color: "blue"
               }
           },
           methods:{

           }
       });
    </script>
</body>

</html>

局部自定义指令

将自定义指令放在组件中变为局部指令，而非之前定义的全局指令。可定义多个自定义指令。

directives:{
    "focus": {
        inserted: function(el){
            el.focus();
        }
    },
    "color": {
        bind: function(el,binding){
            el.style.backgroundColor = binding.value.color;
        }
    }
}

实例：通过局部指令，分别添加光标定位和变化背景色的指令

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <div id="app">
        <input type="text" v-focus v-color="msg">
    </div>
    <script src="js/jquery-3.4.1.js"></script>
    <script src="js/vue.js"></script>
    <script>
        var vm = new Vue({
           el: "#app",
           data: {
               msg:{
                   color: "blue"
               }
           },
           methods:{

           },
           directives:{
               "focus": {
                   inserted: function(el){
                       el.focus();
                   }
               },
               "color": {
                   bind: function(el,binding){
                       el.style.backgroundColor = binding.value.color;
                   }
               }
           }
       });
    </script>
</body>

</html>

计算属性

概述

通过计算属性可以使模板中的表达式更加简洁，将模板中的计算逻辑进行抽取。

计算属性的用法

computed: {
    reverseString: function(){
        return this.msg.split("").reverse().join("");
    }
}

实例：使用计算属性，实现将字符串进行反转的操作。

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <div id="app">
        <div v-text="msg"></div>
        <div v-text="reverseString"></div>
    </div>
    <script src="js/jquery-3.4.1.js"></script>
    <script src="js/vue.js"></script>
    <script>
        var vm = new Vue({
           el: "#app",
           data: {
               msg:"Hello World"
           },
           computed: {
               reverseString: function(){
                   return this.msg.split("").reverse().join("");
               }
           } 
       });
    </script>
</body>

</html>

计算属性与方法的区别

计算属性有缓存，当依赖的数据不发生改变时计算属性仅会被执行一次。
方法没有缓存，每次调用均会执行一次。

实例：通过多次调用，查看计算属性和方法分别被调用的次数。注意调用方法时需要加括号。

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <div id="app">
        <div v-text="msg"></div>
        <div v-text="reverseByComputed"></div>
        <div v-text="reverseByComputed"></div>
        <div v-text="reverseByMethods()"></div>
        <div v-text="reverseByMethods()"></div>
    </div>
    <script src="js/jquery-3.4.1.js"></script>
    <script src="js/vue.js"></script>
    <script>
        var vm = new Vue({
           el: "#app",
           data: {
               msg:"Hello World"
           },
           methods:{
               reverseByMethods: function(){
                    console.log("methods");
                    return this.msg.split("").reverse().join("");
               }
           },
           computed: {
               reverseByComputed: function(){
                   console.log("computed");
                   return this.msg.split("").reverse().join("");
               }
           } 
       });
    </script>
</body>

</html>

监听器

应用场景

当数据变化时执行异步或者开销较大的操作。

监听器用法

watch: {
    firstName: function(val){
        this.fullName = val + "  " + this.lastName;
    },
    lastName: function(val){
        this.fullName = this.firstName + "  " + val;
    }
}

实例：通过监听器，监听姓和名的变化，从而动态改变全名的内容。

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
</head>
<body>
  <div id="app">
    <div>
      <span>名：</span>
      <span>
        <input type="text" v-model='firstName'>
      </span>
    </div>
    <div>
      <span>姓：</span>
      <span>
        <input type="text" v-model='lastName'>
      </span>
    </div>
    <div>{{fullName}}</div>
  </div>
  <script type="text/javascript" src="js/vue.js"></script>
  <script type="text/javascript">
    /*
      侦听器
    */
    var vm = new Vue({
      el: '#app',
      data: {
        firstName: "Yorick",
        lastName: "Jun",
        fullName: "Yorick Jun"
      },
      watch: {
        firstName: function(val){
          this.fullName = val + "  " + this.lastName;
        },
        lastName: function(val){
          this.fullName = this.firstName + "  " + val;
        }
      }
    });
  </script>
</body>
</html>

监听器案例，用于监听输入的改变，进行异步验证

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <div id="app">
      <input type="text" v-model.lazy="uname">
      <span v-text="msg"></span>
    </div>
    <script src="js/jquery-3.4.1.js"></script>
    <script src="js/vue.js"></script>
    <script>
       var vm = new Vue({
           el: "#app",
           data: {
               uname: "",
               msg: ""
           },
           methods: {
                checkName: function(uname){
                    var that = this;
                    setTimeout(function(){
                        if(uname == "yorick"){
                            that.msg = "用户名已被注册，不可使用";
                        }else{
                            that.msg = "用户名可用";
                        }
                    },2000);
                }
           },
           watch: {
               uname: function(val){
                    this.checkName(val);
                    this.msg = "正在验证...";
               }
           }
       });
    </script>
</body>

</html>

过滤器

应用

用于对数据进行格式化操作。

全局自定义过滤器定义语法

Vue.filter("lower",function(val){
    return val.charAt(0).toLowerCase() + val.slice(1);
});

局部自定义过滤器的定义语法

filters: {
    upper: function(val){
        return val.charAt(0).toUpperCase() + val.slice(1);
    }
}

过滤器的使用

1.可以在插值表达式中使用
<div>{{msg | upper}}</div>
2.可以级联使用
<div>{{msg | upper | lower}}</div>
3.可以在属性绑定中使用
<div v-bind:id="id | formatId"></div>

实例：通过过滤器使得数据变为大写和小写开头。

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <div id="app">
        <input type="text" v-model="msg">
        <div>{{msg | upper}}</div>
        <div>{{msg | upper | lower}}</div>
    </div>
    <script src="js/jquery-3.4.1.js"></script>
    <script src="js/vue.js"></script>
    <script>
        // Vue.filter("upper",function(val){
        //     return val.charAt(0).toUpperCase() + val.slice(1);
        // });
        Vue.filter("lower",function(val){
            return val.charAt(0).toLowerCase() + val.slice(1);
        });
       var vm = new Vue({
           el: "#app",
           data: {
             msg: ""
           },
           filters: {
               upper: function(val){
                return val.charAt(0).toUpperCase() + val.slice(1);
               }
           }
       });
    </script>
</body>

</html>

带参数的过滤器

实例：通过带参数的过滤器实现对日期的格式化输出。

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <div id="app">
       <div>{{date | format("yyyy-MM-dd")}}</div>
    </div>
    <script src="js/jquery-3.4.1.js"></script>
    <script src="js/vue.js"></script>
    <script>
        Vue.filter("format",function(val,arg){
            if(arg == "yyyy-MM-dd"){
                var ret = "";
                ret += val.getFullYear() + "-" + (val.getMonth() + 1) + "-" + val.getDate();
                return ret;
            }
            return val;
        });
       var vm = new Vue({
           el: "#app",
           data: {
                date: new Date()
           },
       });
    </script>
</body>

</html>

生命周期

Vue实例的产生需要经过几个生命周期的函数调用。


<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
</head>
<body>
  <div id="app">
    <div>{{msg}}</div>
    <button @click='update'>更新</button>
    <button @click='destroy'>销毁</button>
  </div>
  <script type="text/javascript" src="js/vue.js"></script>
  <script type="text/javascript">
    /*
      Vue实例的生命周期
      
    */
    var vm = new Vue({
      el: '#app',
      data: {
        msg: '生命周期'
      },
      methods: {
        update: function(){
          this.msg = 'hello';
        },
        destroy: function(){
          this.$destroy();
        }
      },
      beforeCreate: function(){
        console.log('beforeCreate');
      },
      created: function(){
        console.log('created');
      },
      beforeMount: function(){
        console.log('beforeMount');
      },
      mounted: function(){
        console.log('mounted');
      },
      beforeUpdate: function(){
        console.log('beforeUpdate');
      },
      updated: function(){
        console.log('updated');
      },
      beforeDestroy: function(){
        console.log('beforeDestroy');
      },
      destroyed: function(){
        console.log('destroyed');
      }
    });
  </script>
</body>
</html>

补充

数组的相关方法，Vue将原生的方法改变为了响应式

变异方法（修改原数据）

push()
pop()
shift()
unshift()
splice()
sort()
reverse()

替换数组（生成新的数组）

filter()
concat()
slice()

实例：通过push(),pop()动态增删列表元素，通过slice()截取元素。


<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
</head>
<body>
  <div id="app">
    <div>
      <span>
        <input type="text" v-model='fname'>
        <button @click='add'>添加</button>
        <button @click='del'>删除</button>
        <button @click='change'>替换</button>
      </span>
    </div>
    <ul>
      <li :key='index' v-for='(item,index) in list'>{{item}}</li>
    </ul>
  </div>
  <script type="text/javascript" src="js/vue.js"></script>
  <script type="text/javascript">
    /*
      Vue数组操作
      1、变异方法：会影响数组的原始数据的变化。
      2、替换数组：不会影响原始的数组数据，而是形成一个新的数组。
    */
    var vm = new Vue({
      el: '#app',
      data: {
        fname: '',
        list: ['apple','orange','banana']
      },
      methods: {
        add: function(){
          this.list.push(this.fname);
        },
        del: function(){
          this.list.pop();
        },
        change: function(){
          this.list = this.list.slice(0,2);
        }
      }
    });
  </script>
</body>
</html>

修改响应式数据

通过以下API方法可以响应式的修改数组或者对象的数据。

Vue.set(vm.list,"1","lemon");
vm.$set(vm.list,"1","lemon");

实例：通过相关API修改数组和对象的属性值


<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
</head>
<body>
  <div id="app">
    <ul>
      <li :key='index' v-for='(item,index) in list'>{{item}}</li>
    </ul>
    <div>{{info.name}}</div>
    <div>{{info.age}}</div>
  </div>
  <script type="text/javascript" src="js/vue.js"></script>
  <script type="text/javascript">
    var vm = new Vue({
      el: '#app',
      data: {
        list: ['apple','orange','banana'],
        info: {
          name: "alice",
          age: 18
        }
      }
    });

    //修改数组的值
    //Vue.set(vm.list,"1","lemon");
    vm.$set(vm.list,"2","lemon");

    //修改对象的值
    // Vue.set(vm.info,"name","bob");
    vm.$set(vm.info,"age",22);
  </script>
</body>
</html>

案例

实现图书管理系统
1.图书的添加，修改，删除功能
2.过滤器格式化时间
3.监听器校验重名
4.自定义指令实现光标定位
5.计算属性实现图书数量的计算
6.生命周期函数实现通过后台服务器获取数据


<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style type="text/css">
    .grid {
      margin: auto;
      width: 530px;
      text-align: center;
    }
    .grid table {
      border-top: 1px solid #C2D89A;
      width: 100%;
      border-collapse: collapse;
    }
    .grid th,td {
      padding: 10;
      border: 1px dashed #F3DCAB;
      height: 35px;
      line-height: 35px;
    }
    .grid th {
      background-color: #F3DCAB;
    }
    .grid .book {
      padding-bottom: 10px;
      padding-top: 5px;
      background-color: #F3DCAB;
    }
    .grid .total {
      height: 30px;
      line-height: 30px;
      background-color: #F3DCAB;
      border-top: 1px solid #C2D89A;
    }
  </style>
</head>
<body>
  <div id="app">
    <div class="grid">
      <div>
        <h1>图书管理</h1>
        <div class="book">
          <div>
            <label for="id">
              编号：
            </label>
            <input type="text" id="id" v-model='id' :disabled="idFlag" v-focus>
            <label for="name">
              名称：
            </label>
            <input type="text" id="name" v-model='name'>
            <button @click='handle' :disabled="submitFlag">提交</button>
          </div>
        </div>
      </div>
      <div class="total">
        <span>图书总数：</span>
        <span>{{total}}</span>
      </div>
      <table>
        <thead>
          <tr>
            <th>编号</th>
            <th>名称</th>
            <th>时间</th>
            <th>操作</th>
          </tr>
        </thead>
        <tbody>
          <tr :key="item.id" v-for="item in books">
            <td>{{item.id}}</td>
            <td>{{item.name}}</td>
            <td>{{item.date | format("yyyy-MM-dd hh:mm:ss")}}</td>
            <td>
              <a href="" @click.prevent="editBook(item.id)">修改</a>
              <span>|</span>
              <a href="" @click.prevent="deleteBook(item.id)">删除</a>
            </td>
          </tr>
        </tbody>
      </table>
    </div>
  </div>
  <script type="text/javascript" src="js/vue.js"></script>
  <script type="text/javascript">
    /*
      图书管理-图书列表展示功能
    */
    //自定义指令，实现光标定位
    Vue.directive("focus",{
      inserted: function(el){
        el.focus();
      }
    });
    //过滤器，实现时间的格式化输出
    Vue.filter('format', function(value, arg) {
      function dateFormat(date, format) {
          if (typeof date === "string") {
              var mts = date.match(/(\/Date\((\d+)\)\/)/);
              if (mts && mts.length >= 3) {
                  date = parseInt(mts[2]);
              }
          }
          date = new Date(date);
          if (!date || date.toUTCString() == "Invalid Date") {
              return "";
          }
          var map = {
              "M": date.getMonth() + 1, //月份 
              "d": date.getDate(), //日 
              "h": date.getHours(), //小时 
              "m": date.getMinutes(), //分 
              "s": date.getSeconds(), //秒 
              "q": Math.floor((date.getMonth() + 3) / 3), //季度 
              "S": date.getMilliseconds() //毫秒 
          };

          format = format.replace(/([yMdhmsqS])+/g, function(all, t) {
              var v = map[t];
              if (v !== undefined) {
                  if (all.length > 1) {
                      v = '0' + v;
                      v = v.substr(v.length - 2);
                  }
                  return v;
              } else if (t === 'y') {
                  return (date.getFullYear() + '').substr(4 - all.length);
              }
              return all;
          });
          return format;
      }
      return dateFormat(value, arg);
    });

    var vm = new Vue({
      el: '#app',
      data: {
        //控制提交按钮是否可用
        submitFlag: false,
        //控制编号输入框是否可用
        idFlag: false,
        id: "",
        name: "",
        books: []
      },
      methods: {
        handle: function(){
          //通过编号输入框是否可用来判别是修改还是添加
          if(this.idFlag){
            //修改
            //使输入框可用
            this.idFlag = false;
            //遍历数组，将对应id的名字做修改
            this.books.some((item)=>{
              if(item.id == this.id){
                item.name = this.name;
                //跳出循环
                return true;
              }
            });
          }else{
            //添加
            var book = {};
            book.id = this.id;
            book.name = this.name;
            book.date = new Date();
            this.books.push(book);
          }
          //清空输入的数据
          this.id = "";
          this.name = "";
        },
        editBook: function(id){
          //查找对应id的对象数组
          var book = this.books.filter(function(item){
            return item.id == id;
          });
          //数据回显到输入框，从数组中取数据，故需要索引
          this.id = book[0].id;
          this.name = book[0].name;
          //设置编号输入框不可用
          this.idFlag = true;
        },
        deleteBook: function(id){
          //将除选中的删除数据外的其他数据重新赋值，实现删除
          this.books = this.books.filter(function(item){
            return item.id != id;
          });
        }
      },
      //计算属性
      computed: {
        total: function(){
          return this.books.length;
        }
      },
      //监听器
      watch: {
        name: function(val){
          //监听到更改的名字与当前数组中的数据有重名，则提交按钮的状态做出对应改变
          var flag = this.books.some(function(item){
            return item.name == val;
          });
          this.submitFlag = flag;
        }
      },
      //通过勾子函数从后台服务器获取数据
      mounted: function(){
        var data = [{
          id: 1,
          name: '三国演义',
          date: new Date()
        },{
          id: 2,
          name: '水浒传',
          date: new Date()
        },{
          id: 3,
          name: '红楼梦',
          date: new Date()
        },{
          id: 4,
          name: '西游记',
          date: new Date()
        }];
        this.books = data;
      }
    });
  </script>
</body>
</html>