Vue2 day02
1.指令的修饰符
其他的也和这个差不多，这里v-model.number文本框里如果输入的是字母显示的也是字母。
2. v-bind操作class
这里注意一下如果是改颜色什么的，不然颜色就要加引号，比如
，不然就改成小驼峰命名
。
3.v-model应用于其他表单元素
4.计算属性
5.computed计算属性vs方法methods
总的来说，methods方法也能执行computed计算属性，但是性能没有那么高，举个例子：
下面是用了computed计算属性的例子：
而用了methods方法
6.计算属性的完整写法
7.成绩案例
<!DOCTYPE html>
<html lang="en"><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" /><link rel="stylesheet" href="./styles/index.css" /><title>Document</title></head><body><div id="app" class="score-case"><div class="table"><table><thead><tr><th>编号</th><th>科目</th><th>成绩</th><th>操作</th></tr></thead><tbody v-if="list.length > 0"><tr v-for="(item, index) in list" :key="item.id"><td>{{ index + 1 }}</td><td>{{ item.subject }}</td><!-- 需求：不及格的标红, < 60 分, 加上 red 类 --><td :class="{ red: item.score < 60 }">{{ item.score }}</td><td><a @click.prevent="del(item.id)" href="http://www.baidu.com">删除</a></td></tr></tbody><tbody v-else><tr><td colspan="5"><span class="none">暂无数据</span></td></tr></tbody><tfoot><tr><td colspan="5"><span>总分：{{ totalScore }}</span><span style="margin-left: 50px">平均分：{{ averageScore }}</span></td></tr></tfoot></table></div><div class="form"><div class="form-item"><div class="label">科目：</div><div class="input"><inputtype="text"placeholder="请输入科目"v-model.trim="subject"/></div></div><div class="form-item"><div class="label">分数：</div><div class="input"><inputtype="text"placeholder="请输入分数"v-model.number="score"/></div></div><div class="form-item"><div class="label"></div><div class="input"><button @click="add" class="submit" >添加</button></div></div></div></div><script src="https://cdn.jsdelivr.net/npm/vue@2/dist/vue.js"></script><script>const app = new Vue({el: '#app',data: {list: [{ id: 1, subject: '语文', score: 62 },{ id: 7, subject: '数学', score: 89 },{ id: 12, subject: '英语', score: 70 },],subject: '',score: ''},computed: {totalScore() {return this.list.reduce((sum, item) => sum + item.score, 0)},averageScore () {if (this.list.length === 0) {return 0}return (this.totalScore / this.list.length).toFixed(2)}},methods: {del (id) {// console.log(id)this.list = this.list.filter(item => item.id !== id)},add () {if (!this.subject) {alert('请输入科目')return}if (typeof this.score !== 'number') {alert('请输入正确的成绩')return}this.list.unshift({id: +new Date(),subject: this.subject,score: this.score})this.subject = ''this.score = ''}}})</script></body>
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8.watch-简写-语法
<!DOCTYPE html>
<html lang="en"><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>Document</title><style>* {margin: 0;padding: 0;box-sizing: border-box;font-size: 18px;}#app {padding: 10px 20px;}.query {margin: 10px 0;}.box {display: flex;}textarea {width: 300px;height: 160px;font-size: 18px;border: 1px solid #dedede;outline: none;resize: none;padding: 10px;}textarea:hover {border: 1px solid #1589f5;}.transbox {width: 300px;height: 160px;background-color: #f0f0f0;padding: 10px;border: none;}.tip-box {width: 300px;height: 25px;line-height: 25px;display: flex;}.tip-box span {flex: 1;text-align: center;}.query span {font-size: 18px;}.input-wrap {position: relative;}.input-wrap span {position: absolute;right: 15px;bottom: 15px;font-size: 12px;}.input-wrap i {font-size: 20px;font-style: normal;}</style></head><body><div id="app"><!-- 条件选择框 --><div class="query"><span>翻译成的语言：</span><select><option value="italy">意大利</option><option value="english">英语</option><option value="german">德语</option></select></div><!-- 翻译框 --><div class="box"><div class="input-wrap"><textarea v-model="obj.words"></textarea><span><i>⌨️</i>文档翻译</span></div><div class="output-wrap"><div class="transbox">mela</div></div></div></div><script src="https://cdn.jsdelivr.net/npm/vue@2/dist/vue.js"></script><script src="https://cdn.jsdelivr.net/npm/axios/dist/axios.min.js"></script><script>// 接口地址：https://applet-base-api-t.itheima.net/api/translate// 请求方式：get// 请求参数：// （1）words：需要被翻译的文本（必传）// （2）lang： 需要被翻译成的语言（可选）默认值-意大利// -----------------------------------------------const app = new Vue({el: '#app',data: {// words: ''obj: {words: ''}},// 具体讲解：(1) watch语法 (2) 具体业务实现watch: {// 该方法会在数据变化时调用执行// newValue新值, oldValue老值（一般不用）// words (newValue) {// console.log('变化了', newValue)// }'obj.words' (newValue) {console.log('变化了', newValue)}}})</script></body>
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9.watch-简写-业务实现
<!DOCTYPE html>
<html lang="en"><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>Document</title><style>* {margin: 0;padding: 0;box-sizing: border-box;font-size: 18px;}#app {padding: 10px 20px;}.query {margin: 10px 0;}.box {display: flex;}textarea {width: 300px;height: 160px;font-size: 18px;border: 1px solid #dedede;outline: none;resize: none;padding: 10px;}textarea:hover {border: 1px solid #1589f5;}.transbox {width: 300px;height: 160px;background-color: #f0f0f0;padding: 10px;border: none;}.tip-box {width: 300px;height: 25px;line-height: 25px;display: flex;}.tip-box span {flex: 1;text-align: center;}.query span {font-size: 18px;}.input-wrap {position: relative;}.input-wrap span {position: absolute;right: 15px;bottom: 15px;font-size: 12px;}.input-wrap i {font-size: 20px;font-style: normal;}</style>
</head><body><div id="app"><!-- 条件选择框 --><div class="query"><span>翻译成的语言：</span><select><option value="italy">意大利</option><option value="english">英语</option><option value="german">德语</option></select></div><!-- 翻译框 --><div class="box"><div class="input-wrap"><textarea v-model="obj.words"></textarea><span><i>⌨️</i>文档翻译</span></div><div class="output-wrap"><div class="transbox">{{ result }}</div></div></div></div><script src="https://cdn.jsdelivr.net/npm/vue@2/dist/vue.js"></script><script src="https://cdn.jsdelivr.net/npm/axios/dist/axios.min.js"></script><script>// 接口地址：https://applet-base-api-t.itheima.net/api/translate// 请求方式：get// 请求参数：// （1）words：需要被翻译的文本（必传）// （2）lang： 需要被翻译成的语言（可选）默认值-意大利// -----------------------------------------------const app = new Vue({el: '#app',data: {// words: ''obj: {words: ''},result: '', // 翻译结果// timer: null // 延时器id},// 具体讲解：(1) watch语法 (2) 具体业务实现watch: {// 该方法会在数据变化时调用执行// newValue新值, oldValue老值（一般不用）// words (newValue) {// console.log('变化了', newValue)// }'obj.words'(newValue) {// console.log('变化了', newValue)// 防抖: 延迟执行 → 干啥事先等一等，延迟一会，一段时间内没有再次触发，才执行clearTimeout(this.timer)this.timer = setTimeout(async () => {const res = await axios({url: 'https://applet-base-api-t.itheima.net/api/translate',params: {words: newValue}})this.result = res.data.dataconsole.log(res.data.data)}, 300)}}})</script>
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10.watch-完整写法
11.水果购物车-基本渲染
先补充一些用法：
<!DOCTYPE html>
<html lang="en"><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" /><link rel="stylesheet" href="./css/inputnumber.css" /><link rel="stylesheet" href="./css/index.css" /><title>购物车</title></head><body><div class="app-container" id="app"><!-- 顶部banner --><div class="banner-box"><img src="http://autumnfish.cn/static/fruit.jpg" alt="" /></div><!-- 面包屑 --><div class="breadcrumb"><span>🏠</span>/<span>购物车</span></div><!-- 购物车主体 --><div class="main" v-if="fruitList.length > 0"><div class="table"><!-- 头部 --><div class="thead"><div class="tr"><div class="th">选中</div><div class="th th-pic">图片</div><div class="th">单价</div><div class="th num-th">个数</div><div class="th">小计</div><div class="th">操作</div></div></div><!-- 身体 --><div class="tbody"><div v-for="(item, index) in fruitList" :key="item.id" class="tr" :class="{ active: item.isChecked }"><div class="td"><input type="checkbox" v-model="item.isChecked" /></div><div class="td"><img :src="item.icon" alt="" /></div><div class="td">{{ item.price }}</div><div class="td"><div class="my-input-number"><button :disabled="item.num <= 1" class="decrease" @click="sub(item.id)"> - </button><span class="my-input__inner">{{ item.num }}</span><button class="increase" @click="add(item.id)"> + </button></div></div><div class="td">{{ item.num * item.price }}</div><div class="td"><button @click="del(item.id)">删除</button></div></div></div></div><!-- 底部 --><div class="bottom"><!-- 全选 --><label class="check-all"><input type="checkbox" v-model="isAll"/>全选</label><div class="right-box"><!-- 所有商品总价 --><span class="price-box">总价 : ¥ <span class="price">{{ totalPrice }}</span></span><!-- 结算按钮 --><button class="pay">结算( {{ totalCount }} )</button></div></div></div><!-- 空车 --><div class="empty" v-else>🛒空空如也</div></div><script src="https://cdn.jsdelivr.net/npm/vue@2/dist/vue.js"></script><script>const defaultArr = [{id: 1,icon: 'http://autumnfish.cn/static/火龙果.png',isChecked: true,num: 2,price: 6,},{id: 2,icon: 'http://autumnfish.cn/static/荔枝.png',isChecked: false,num: 7,price: 20,},{id: 3,icon: 'http://autumnfish.cn/static/榴莲.png',isChecked: false,num: 3,price: 40,},{id: 4,icon: 'http://autumnfish.cn/static/鸭梨.png',isChecked: true,num: 10,price: 3,},{id: 5,icon: 'http://autumnfish.cn/static/樱桃.png',isChecked: false,num: 20,price: 34,},]const app = new Vue({el: '#app',data: {// 水果列表fruitList: JSON.parse(localStorage.getItem('list')) || defaultArr,},computed: {// 默认计算属性：只能获取不能设置，要设置需要写完整写法// isAll () {// // 必须所有的小选框都选中，全选按钮才选中 → every// return this.fruitList.every(item => item.isChecked)// }// 完整写法 = get + setisAll: {get () {return this.fruitList.every(item => item.isChecked)},set (value) {// 基于拿到的布尔值，要让所有的小选框 同步状态this.fruitList.forEach(item => item.isChecked = value)}},// 统计选中的总数 reducetotalCount () {return this.fruitList.reduce((sum, item) => {if (item.isChecked) {// 选中 → 需要累加return sum + item.num} else {// 没选中 → 不需要累加return sum}}, 0)},// 总计选中的总价 num * pricetotalPrice () {return this.fruitList.reduce((sum, item) => {if (item.isChecked) {return sum + item.num * item.price} else {return sum}}, 0)}},methods: {del (id) {this.fruitList = this.fruitList.filter(item => item.id !== id)},add (id) {// 1. 根据 id 找到数组中的对应项 → findconst fruit = this.fruitList.find(item => item.id === id)// 2. 操作 num 数量fruit.num++},sub (id) {// 1. 根据 id 找到数组中的对应项 → findconst fruit = this.fruitList.find(item => item.id === id)// 2. 操作 num 数量fruit.num--}},watch: {fruitList: {deep: true,handler (newValue) {// 需要将变化后的 newValue 存入本地 （转JSON）localStorage.setItem('list', JSON.stringify(newValue))}}}})</script></body>
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