<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<title>计算属性和侦听器</title>
<meta name="viewport" content="width=device-width, initial-scale=1">
<script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
</head>
<body>
<div id="app">
<p>Original message: "{{ message }}"</p>
<p>Computed reversed message: "{{ reversedMessage__() }}"</p>
</div>
<div id="watch-example">
<p>
Ask a yes/no question:
<input v-model="question">
</p>
<p>{{ answer }}</p>
</div>
</body>
</html>
<script src="https://cdn.jsdelivr.net/npm/axios@0.12.0/dist/axios.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/lodash@4.13.1/lodash.min.js"></script>
<script>
var watchExampleVM = new Vue({
el: '#watch-example',
data: {
question: '',
answer: 'I cannot give you an answer until you ask a question!'
},
watch: {
// 如果 `question` 发生改变，这个函数就会运行
question: function (newQuestion, oldQuestion) {
this.answer = 'Waiting for you to stop typing...'
this.debouncedGetAnswer()
}
},
created: function () {
// `_.debounce` 是一个通过 Lodash 限制操作频率的函数。
// 在这个例子中，我们希望限制访问 yesno.wtf/api 的频率
// AJAX 请求直到用户输入完毕才会发出。想要了解更多关于
// `_.debounce` 函数 (及其近亲 `_.throttle`) 的知识，
// 请参考：https://lodash.com/docs#debounce
this.debouncedGetAnswer = _.debounce(this.getAnswer, 500)
},
methods: {
getAnswer: function () {
if (this.question.indexOf('?') === -1) {
this.answer = 'Questions usually contain a question mark. ;-)'
return
}
this.answer = 'Thinking...'
var vm = this
axios.get('https://yesno.wtf/api')
.then(function (response) {
vm.answer = _.capitalize(response.data.answer)
})
.catch(function (error) {
vm.answer = 'Error! Could not reach the API. ' + error
})
}
}
})
</script>
<script>
var vm = new Vue({
el: '#app',
data: {
message: 'Hello'
},
computed: {
// 计算属性的 getter
reversedMessage: function () {
// `this` 指向 vm 实例
return this.message.split('').reverse().join('')
},
//显示的增加计算属性的set 和 get 方法
/* 比较神奇的是 如果get方法中用到了data里面的属性 如果data里面属性变更则计算属性会跟着变 */
reversedMessage_: {
get: function () {
return this.message.split('').reverse().join('')+ '-max-'
},
set: function (v) {
return this.message + 'rand'
}
}
},
methods: {
reversedMessage__ :function(){
return this.message.split('').reverse().join('')+ Date.now()
}
},
})
console.log(vm);
</script>