The applet cloud function updates the specified position element of the array

The way written in the cloud development document is to write the field name 'array.0' if the first one is updated. Such as:

But I want to update the key attribute of the i-th element of an array (stored in an object), i is a parameter, and I currently use the template string `array.${i}.key` and the string splicing 'array .'+i+'.key', neither of these methods will work.

After seeing the first solution in this tutorial , I found a solution!

Use the $ positional placeholder:

exports.main = async(event, context) => {
    return db.collection('user').where({
        '_id':event.docID,
        'array.key': event.key
    }).update({
        data: {
            'array.$.key': event.value,
            arrNum: _.inc(1)
        },
        success: res => {
            console.log(res)
        }
    })
}

where can not only find documents, but also find the position of eligible elements in an array in the document!
Then use the $ symbol that stores the position data to update the properties of the i-th element in the array.

My original answer: How does the cloud function update the specified array element? - WeChat open community https://developers.weixin.qq.com/community/develop/doc/0000e479ca4890c7be1941bbc5b800