为啥我这 wx:for-index设置后 e 获取不到这个index的值？

<view wx:for=“array” wx:for-index=“idx” wx:key bindtap=“bbb”>

{{idx}}: {{itemName.message}}

</view>

页面是有显示idx的值但是为啥e获取不到这个idx

bbb(e){

console.log(e)

},

1. 
   

2. 
   

3. {type: "tap", timeStamp: 19646, target: {…}, currentTarget: {…}, mark: {…}, …}

1. changedTouches: [{…}]

2. currentTarget: {id: "", offsetLeft: 0, offsetTop: 20, dataset: {…}}

3. detail: {x: 38, y: 32}

4. mark: {}

5. mut: false

6. target: {id: "", offsetLeft: 0, offsetTop: 20, dataset: {…}}

7. timeStamp: 19646

8. touches: [{…}]

9. type: "tap"

10. __proto__: Object