db.command.aggregate.isArray

1. Operator Description

Function: Determines whether a given expression is an array and returns a boolean value.

Declaration: db.command.aggregate.isArray(expression)

2. Operator Parameters

Field	Type	Required	Description
-	Expression	Required	The parameter can be any aggregate expression.

3. Sample Code

Suppose the collection stats contains the following records:

{
  "_id": 1,
  "base": 10,
  "sales": [ 1, 6, 2, 2, 5 ]
}
{
  "_id": 2,
  "base": 1,
  "sales": 100
}

Calculate the total sales: if sales is a number, compute sales * base; if sales is an array, compute the product of the sum of the array elements and base.

// 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('stats')
    .aggregate()
    .project({
      sum: $.cond({
        if: $.isArray('$sales'),
        then: $.multiply([$.sum(['$sales']), '$base']),
        else: $.multiply(['$sales', '$base'])
      })
    })
    .end()
  console.log(res.data)
}

The returned result is as follows:

{ "_id": 1, "index": 160 }
{ "_id": 2, "index": 100 }