data中的數據：
data:{
days:[
{title:'昨天'，methods:'dayBefore'},
{title:'今天'，methods:'today'},
{title:'近7天'，methods:firstSevenDays},
{title:'近30天'，methods:'firstThirtyDays'},
]
},
methods:{
getDays：function(methodsWords){ //關鍵字
this[methodsWords]();
}，
dayBefore：function(){
console.log("dayBefore")
} ,
firstSevenDays：function(){
console.log("firstSevenDays")
} ,
today：function(){
console.log("today")
} ,
firstThirtyDays：function(){
console.log("firstThirtyDays")
} ,
}
html:
<ul>
<li v-for="(day,index) in days" class="days" @click="getDays(day.methods)"></li>
</ul>