Detailed explanation of the usage and differences of computed, filter, get and set in vue.js-JS Tutorial-php.cn

Detailed explanation of the usage and differences of computed, filter, get and set in vue.js

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Release： 2018-05-31 17:17:08

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Below I will share with you a detailed explanation of the usage and differences of computed, filter, get, and set in vue.js. It has a good reference value and I hope it will be helpful to everyone.

1. The computed method of vue.js:

handles complex logic, based on dependency caching, and will re-value when dependencies change. . The same effect can be achieved using methods, but methods will be re-invoked and executed when re-rendering. Computed is better than methods in terms of performance. Methods can be used when caching is not needed.

Example 1: computed and methods implement flipping string

<template>
 <p>
 <input v-model="message">
 <p>原始字符串: {{ message }}</p>
 <p>计算后反转字符串: {{ reversedMessage }}</p>
 <p>使用方法后反转字符串: {{ reversedMessage2() }}</p>
 </p>
</template>

<script>
export default {
 data () {
 return {
 message: &#39;Runoob123!&#39;
 }
 },
 computed: {
 // 计算属性的 getter
 reversedMessage: function () {
 // `this` 指向 vm 实例
 return this.message.split(&#39;&#39;).reverse().join(&#39;&#39;)
 }
 },
 methods: {
 reversedMessage2: function () {
 return this.message.split(&#39;&#39;).reverse().join(&#39;&#39;)
 }
 }
}
</script>

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Execution results:

Example 2: Computed get() and set() usage

<template>
 <p>
 	<select v-model="site">
 		<option value="Google http://www.google.com">Google http://www.google.com</option>
 		<option value="baidu http://www.baidu.co">baidu http://www.baidu.com</option>
 		<option value="网易 http://www.163.com">网易 http://www.163.com</option>
 	</select>
 	<p>name：{{name}}</p>
 	<p>url：{{url}}</p>
 </p>
</template>

<script>
export default {
 data () {
 return {
 name: &#39;Google&#39;,
 url: &#39;http://www.google.com&#39;
 }
 },
 computed: {
 site: {
 // getter
 get: function () {
 return this.name + &#39; &#39; + this.url
 },
 // setter
 set: function (newValue) {
 let names = newValue.split(&#39; &#39;)
 this.name = names[0]
 this.url = names[names.length - 1]
 }
 }
 }
}
</script>

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Execution result:

2. Filter method of vue.js:

A filter is a simple function that processes the returned data and returns the processing result. However, it was removed in the vue2.0 version. The alternative is to write the function in methods.

Example:

<template>
 <p>
 <input v-model="filterText"/>
 <ul>
 <li v-for="item in obj">
 <span>{{myfilter(item.label)}}</span>
 </li>
 </ul>
 </p>
</template>

<script>
export default {
 data () {
 return {
 obj: [
 {value: 0, label: &#39;beijing&#39;},
 {value: 1, label: &#39;shanghai&#39;},
 {value: 2, label: &#39;guangdong&#39;},
 {value: 3, label: &#39;zhejiang&#39;},
 {value: 4, label: &#39;jiangshu&#39;}
 ],
 filterText: &#39;&#39;
 }
 },
 methods: {
 myfilter (value) {
 if (value.indexOf(this.filterText) > -1) {
 return value
 }
 }
 }
}
</script>

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Execution result:

3. The get and set methods of vue.js:

The data attribute in vue can respond to data changes. Internally, the data attribute is converted into a getter/setter. In vue2.0, get() and set() are used in computed properties, which have been covered in the computed instance above. In addition, vm.$set(object, key, value) inherited from vue1.0 is used to dynamically monitor data elements. After the instance is created, array attributes are added and responses can be implemented using this method.

<template>
 <p>
 <input v-model="opt" @blur="add()"/>
 <ul>
 <li v-for="item in arr">
 {{ item }}
 </li>
 </ul>
 </p>
</template>

<script>
export default {
 data () {
 return {
 arr: [ &#39;北京&#39;, &#39;上海&#39;, &#39;广东&#39;, &#39;深圳&#39; ],
 opt: &#39;&#39;
 }
 },
 methods: {
 add () {
 this.$set(this.arr, this.arr.length, this.opt)
 }
 }
}
</script>

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Execution results:

The above is what I compiled for everyone. I hope it will be useful to everyone in the future. helpful.

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