微信小程序动态修改data里面的值

<view>
  <block wx:for="{{test}}" wx:key="*this">
    <button type='primary' size='mini' bindtap='chageval' data-id='{{item.id}}'>{{item.name}}</button>
    <text>{{item.val}}</text>
  </block>
</view>

test: [
  {
    id: 1,
    name: 'wangyu',
    val: '123'
  },
  {
    id: 2,
    name: 'mayan',
    val: '456'
  }
]
chageval(e){
  var x = e.currentTarget.dataset.id;
  console.log(x);
  var str = "test[" + (x-1) + "].val";
  this.setData({
    [str]: 'aaa'+x
  });
}