步骤 1 : 先看不用 computed
<script src="http://how2j.cn/study/vue.min.js"></script>
<style>
table tr td{
border:1px solid gray;
padding:10px;
}
table{
border-collapse:collapse;
width:800px;
table-layout:fixed;
}
tr.firstLine{
background-color: lightGray;
}
</style>
<div id="div1">
<table align="center" >
<tr class="firstLine">
<td>人民币</td>
<td>美元</td>
</tr>
<tr>
<td align="center" colspan="2">
汇率: <input type="number" v-model.number="exchange" />
</td>
</tr>
<tr>
<td align="center">
¥: <input type="number" v-model.number = "rmb" />
</td>
<td align="center">
$: {{ rmb/exchange }}
</td>
</tr>
</table>
</div>
<script>
new Vue({
el: '#div1',
data: {
exchange:6.4,
rmb:0
}
})
</script>
步骤 2 : 再看看 computed 的做法
<script src="http://how2j.cn/study/vue.min.js"></script>
<style>
table tr td{
border:1px solid gray;
padding:10px;
}
table{
border-collapse:collapse;
width:800px;
table-layout:fixed;
}
tr.firstLine{
background-color: lightGray;
}
</style>
<div id="div1">
<table align="center" >
<tr class="firstLine">
<td>人民币</td>
<td>美元</td>
</tr>
<tr>
<td align="center" colspan="2">
汇率: <input type="number" v-model.number="exchange" />
</td>
</tr>
<tr>
<td align="center">
¥: <input type="number" v-model.number = "rmb" />
</td>
<td align="center">
$: {{ dollar }}
</td>
</tr>
</table>
</div>
<script>
new Vue({
el: '#div1',
data: {
exchange:6.4,
rmb:0
},
computed:{
dollar:function() {
return this.rmb / this.exchange;
}
}
})
</script>
步骤 3 : methods 也能达到一样的效果
<script src="http://how2j.cn/study/vue.min.js"></script>
<style>
table tr td{
border:1px solid gray;
padding:10px;
}
table{
border-collapse:collapse;
width:800px;
table-layout:fixed;
}
tr.firstLine{
background-color: lightGray;
}
</style>
<div id="div1">
<table align="center" >
<tr class="firstLine">
<td>人民币</td>
<td>美元</td>
</tr>
<tr>
<td align="center" colspan="2">
汇率: <input type="number" v-model.number="exchange" />
</td>
</tr>
<tr>
<td align="center">
¥: <input type="number" v-model.number = "rmb" />
</td>
<td align="center">
$: {{ getDollar() }}
</td>
</tr>
</table>
</div>
<script>
new Vue({
el: '#div1',
data: {
exchange:6.4,
rmb:0
},
methods:{
getDollar:function() {
return this.rmb / this.exchange;
}
}
})
</script>
步骤 4 : computed 和 methods 的区别
computed 是有缓存的,只要rmb没有变化,dollar 会直接返回以前计算出来的值,而不会再次计算。 这样如果是复杂计算,就会节约不少时间。
而methods每次都会调用