- computed和methods
在vue.js中，有methods和computed两种方式来动态当作方法来用的:首先最明显的不同 就是调用的时候，methods要加上（）;我们可以使用 methods 来替代 computed，效果上两个都是一样的，但是 computed 是基于它的依赖缓存，只有相关依赖发生改变时才会重新取值。而使用 methods ，在重新渲染的时候，函数总会重新调用执行
- 代码
<html>
<head>
<meta charset="utf-8" />
<title></title>
<title>computed练习</title>
<!-- 开发环境版本，包含了有帮助的命令行警告 -->
<script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
</head>
<body>
<!-- vue-app的根容器 -->
<div id="app">
<button type="button" @click="show2">调用methods</button>
<button tuype="button" @click="show1">调用computed</button>
</div>
<script type="text/javascript">
var app=new Vue({
el:'#app',
data:{
name1:'methods',
name2:'这是Vue.jsd的computed计算练习'
},
methods:{
show2:function(){
alert(this.name1);
}
},
computed:{
show:function(){
alert(this.name2);
}
}
})
</script>
</body>
</html>
- 简单购物车
<html>
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1">
<title></title>
<title>购物车练习</title>
<!-- 开发环境版本，包含了有帮助的命令行警告 -->
<script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
<style type="text/css">
.a{
width: 40%;
margin: 0 auto;
}
.container{
display: flex;
flex-direction: column;
}
.item{
display: flex;
border: 1px solid #008000;
border-radius: 10px;
width: 350px;
height: 50px;
margin-bottom: 10px;
/* 垂直方向居中 */
align-items: center;
/* 水平方向居中 */
/* justify-content: center; */
padding-left: 10px;
padding-right: 10px;
}
.item-id{
flex: 1 1 20%;
}
.item-name{
flex: 1 1 20%;
}
.item-price{
flex: 1 1 30%;
}
.item-count{
/* display: flex; */
flex: 1 1 30%;
}
.goods-count{
width: 15px;
}
.btn{
border: 1px #3083ff solid;
border-radius: 4px;
background-color: #3487ff;
box-shadow: 0 5px 8px 0 rgba(24,95,255,.1);
color: #fff;
text-align: center;
font-weight: lighter;
background-image: linear-gradient(0deg,#398bff,#3083ff);
width: 60px;
height: 40px;
/* margin: 40px 0 8px; */
font-size: 18px;
}
img{
width: 45px;
height: 45px;
}
.item-img{
flex: 1 1 30%;
}
.commit{
width: 350px;
display: flex;
justify-content: space-between;
align-content: center;
}
a:link{
text-decoration: none;
}
</style>
</head>
<body>
<!-- vue-app的根容器 -->
<div id="app" class="a">
<div class="container">
<div class="item" v-for="goods in goodsList">
<div class="item-id" >
{{goods.id}}
</div>
<div class="item-name">
<a :href="goods.url">
{{goods.name}}
</a>
</div>
<div class="item-img">
<img :src="goods.image" />
</div>
<div class="item-price">
{{goods.price}}
</div>
<div class="item-count">
<button type="button" @click="goods.count-=1"
:disabled="goods.count===0">-</button>
<input type="text" v-model="goods.count" class="goods-count"/>
<button type="button" @click="goods.count+=1">+</button>
</div>
</div>
</div>
<hr/>
<div class="commit">
<p>总价：￥{{totalPrice}}</p>
<button type="button" class="btn" @click="settl">结算</button>
</div>
</div>
<script type="text/javascript">
var app=new Vue({
el:'#app',
data:{
goodsList:[{
id:1,
name:'iPhone7',
price:5000,
count:1,
image:'img/iPhone7-2.jpg',
url:'https://item.jd.com/3133811.html'
},
{
id:2,
name:'iPhoneX',
price:7000,
count:2,
image:'img/iPhoneX.jpg',
url:'https://item.jd.com/5089253.html'
},
{
id:3,
name:'iPhone8',
price:6000,
count:1,
image:'img/iPhone8.jpg',
url:'https://item.jd.com/5089269.html'
}
]
},
methods:{
settl:function(){
alert("您好，您本次购买手机"+this.totalCount+"部,共消费"+this.totalPrice+"元。");
}
},
computed:{
totalPrice:function(){
var totalPrice=0;
var len=this.goodsList.length;
for(var i=0;i<len;i++){
totalPrice += this.goodsList[i].price*this.goodsList[i].count;
}
return totalPrice;
},
totalCount: function() {
this.show = true;
var totalCount = 0;
var len = this.goodsList.length;
for (var i = 0; i < len; i++) {
totalCount += this.goodsList[i].count;
}
return totalCount;
}
}
})
</script>
</body>
</html>
效果图：
day07-1.png
- 文章搜索
<html>
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1">
<title>搜索页面的实现</title>
<script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
<style type="text/css">
.container {
width: 60%;
margin: 0 auto;
}
.input-box {
width: 50%;
height: 25px;
margin-bottom: 10px;
}
.btn{
width: 50px;
height: 25px;
border: 1px #3083ff solid;
border-radius: 4px;
background-color: #3487ff;
box-shadow: 0 5px 8px 0 rgba(24,95,255,.1);
text-align: center;
font-weight: lighter;
background-image: linear-gradient(0deg,#398bff,#3083ff);
font-size: 18px;
margin-bottom: 10px;
}
.item {
display: flex;
height: 100px;
border: 1px solid #eee;
border-radius: 8px;
margin-bottom: 8px;
}
.item-title {
flex: 1 1 80%;
}
.item-thumbnail {
flex: 1 1 20%
}
.item-thumbnail img {
width: 100%;
height: 100%;
}
a:link{
color:#333333;
text-decoration: none;
}
</style>
</head>
<body>
<div id="app">
<div class="container">
<input type="text" v-model="searchString" placeholder="请输入" class="input-box" />
<!-- <button type="button" class="btn" @click="filteredArticles">搜索</button> -->
<div class="item" v-for="article in filteredArticles">
<a :href="article.url" class="item-title">
{{article.title}}
</a>
<div class="item-thumbnail">
<img :src="article.image">
</div>
</div>
</div>
</div>
<script type="text/javascript">
var app = new Vue({
el: '#app',
data: {
searchString: "",
// 数据模型
articles: [{
"title": "堪称神器的3款在线工具，你一定用得上！",
"url": "https://www.jianshu.com/p/e83e7999346b",
"image": "https://upload-images.jianshu.io/upload_images/11438996-56b25f32c9307b4b?imageMogr2/auto-orient/strip%7CimageView2/2/w/640/format/webp"
},
{
"title": "经典面试题：从 URL 输入到页面展现到底发生什么？",
"url": "https://www.jianshu.com/p/45ba3e0d0c7e",
"image": "https://upload-images.jianshu.io/upload_images/3973862-d90954249a6f6ccd.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1000/format/webp"
},
{
"title": "如何免翻墙使用谷歌搜索和Chrome应用商店",
"url": "https://www.jianshu.com/p/484f8e6c88f6",
"image": "https://upload-images.jianshu.io/upload_images/858154-015a4b083685a3d1.jpg?imageMogr2/auto-orient/strip%7CimageView2/2/w/800/format/webp"
},
{
"title": "四款前所未有好用的黑科技APP，绝对的良心实用，赶紧告诉家人",
"url": "https://www.jianshu.com/p/2aec84d269fe",
"image": "https://upload-images.jianshu.io/upload_images/16042993-168b2cb17fd7ec0c?imageMogr2/auto-orient/strip%7CimageView2/2/w/640/format/webp"
},
{
"title": "坚持学英语的方法有哪些",
"url": "https://www.jianshu.com/p/0a6a61b0933c",
"image": "https://upload-images.jianshu.io/upload_images/3525704-c7293758fc59e56b.jpg?imageMogr2/auto-orient/strip%7CimageView2/2/w/960/format/webp"
}
]
},
computed: {
// 计算函数，匹配搜索
filteredArticles: function() {
var articles_array = this.articles,
searchString = this.searchString;
//搜索关键词为空,则返回原始数据集
if (!searchString) {
return articles_array;
}
//搜索关键词去除无用空格,转换为小写
searchString = searchString.trim().toLowerCase();
//过滤数组中每个元素
articles_array = articles_array.filter(function(item) {
if (item.title.toLowerCase().indexOf(searchString) !== -1) {
return item;
}
})
// 返回转化后的数组
return articles_array;;
}
}
})
</script>
</body>
</html>
效果图：
day07-2.png
day07-3.png
