小程序wx:key的使用

<switch wx:for="{{objectArray}}" wx:key="unique" style="display: block;"> {{item.id}} </switch>
<button bindtap="switch"> Switch </button>
<button bindtap="addToFront"> Add to the front </button>

<switch wx:for="{{numberArray}}" wx:key="*this" style="display: block;"> {{item}} </switch>
<button bindtap="addNumberToFront"> Add to the front </button>

Page({
      data: {
        objectArray: [
          { id: 5, unique: 'unique_5' },
          { id: 4, unique: 'unique_4' },
          { id: 3, unique: 'unique_3' },
          { id: 2, unique: 'unique_2' },
          { id: 1, unique: 'unique_1' },
          { id: 0, unique: 'unique_0' },
        ],
        numberArray: [1, 2, 3, 4]
      },

      switch: function (res) {
        const len = this.data.objectArray.length
        console.log(len)
        for (let i = 0; i < len; ++i) {
          const x = Math.floor(Math.random() * len)   // 0至5
          const y = Math.floor(Math.random() * len)   // 0至5
          const temp = this.data.objectArray[x]
          this.data.objectArray[x] = this.data.objectArray[y]
          this.data.objectArray[y] = temp
        }
        this.setData({
          objectArray: this.data.objectArray
        })
      },


      addToFront: function (res) {
        const len = this.data.objectArray.length
        this.data.objectArray = [{ id: len, unique: 'unique_' + len }].concat(this.data.objectArray)
        this.setData({
          objectArray: this.data.objectArray
        })
      },

      addNumberToFront: function (res) {
        this.data.numberArray = [this.data.numberArray.length + 1].concat(this.data.numberArray)
        this.setData({
          numberArray: this.data.numberArray
        })
      },

    })