Vue中v-for更新检测的操作方法

let arr = [1,2,3,4,5]
console.log(arr.splice(2,2))     //[3,4]
console.log(arr)    // [1,2,5]

let arr = [2,10,6,1,4,22,3]
console.log(arr.sort())   // [1, 10, 2, 22, 3, 4, 6]
let arr1 = arr.sort((a, b) =>a - b)  
console.log(arr1)   // [1, 2, 3, 4, 6, 10, 22]
let arr2 = arr.sort((a, b) =>b-a)  
console.log(arr2)  // [22, 10, 6, 4, 3, 2, 1]

let arr = [1,2,3,4,5]
console.log(arr.reverse())    // [5,4,3,2,1]
console.log(arr)    // [5,4,3,2,1]

let arr = [1,2,3,4,5]
console.log(arr.concat([1,2]))  // [1,2,3,4,5,1,2]
console.log(arr)   // [1,2,3,4,5]

let arr = [1,2,3,4,5]
console.log(arr.slice(1,3))   // [2,3]

<li v-for="(val, index) in arr" :key="index">
     {{ val }}
   </li>
   <button @click="sliceBtn">截取前3个</button>
   
    sliceBtn(){
   // 2. 数组slice方法不会造成v-for更新
   // slice不会改变原始数组
   // this.arr.slice(0, 3)

   // 解决v-for更新 - 覆盖原始数组
   let newArr = this.arr.slice(0, 3)
   this.arr = newArr
 },

<li v-for="(val, index) in arr" :key="index">
     {{ val }}
   </li>
   <button @click="sliceBtn">更新下标0的值</button>
   
   sliceBtn(){
   // 更新某个值时，v-for是检测不到的
   // this.arr[0] = 1000
   
   // 解决- this.$set()
   // 参数1：更新目标结构
   // 参数2：更新位置
   // 参数3：更新值
   let newArr = this.arr.slice(0, 3)
   this.arr = newArr
 },