db.command.aggregate.strLenBytes

1. Operator Description

Function: Calculates and returns the number of bytes in the specified string under utf-8 encoding.

Declaration: db.command.aggregate.strLenBytes(<expression>)

2. Operator Parameters

Field	Type	Required	Description
-	Expression	Required	aggregate expression that can be resolved to a string

3. Sample Code

Suppose the collection students contains the following records:

{ "name": "dongyuanxin", "nickname": "Xin Tan" }

Use strLenBytes to calculate the byte length of the values corresponding to the name and nickname fields:

// Sample code in the Cloud Function environment
const tcb = require('@cloudbase/node-sdk')
const app = tcb.init({
  env: 'xxx'
})

const db = app.database()
const $ = db.command.aggregate
const _ = db.command

exports.main = async (event, context) => {
  const res = await db
    .collection('students')
    .aggregate()
    .project({
      _id: 0,
      nameLength: $.strLenBytes('$name'),
      nicknameLength: $.strLenBytes('$nickname')
    })
    .end()
  console.log(res.data)
}

The returned result is as follows:

{ "nameLength": 11, "nicknameLength": 6 }