AWS Pinpoint sendMessages() Addresses param field error

I'm having trouble replicating the format of the params object's Addresses format in a way where I can easily add to the object.

If I use this as the params with destinationNumber[0] and destinationNumber[1] in the format of 1 + 9 digit number ie 13334535667 then it sends the message to both numbers no problem.

 const params = {
        ApplicationId: applicationId,
        MessageRequest: {
            Addresses: {
                [destinationNumber[0]]: {
                    ChannelType: 'SMS'
                },
                [destinationNumber[1]]: {
                    ChannelType: 'SMS'
                }
            },
            MessageConfiguration: {
                SMSMessage: {
                    Body: message,
                    Keyword: registeredKeyword,
                    MessageType: messageType,
                    OriginationNumber: originationNumber
                }
            }
        }
    };

I'm trying to replicate this format for Addresses, but I'm getting Unexpected key '13334535667' found in params.MessageRequest.Addresses['0']. The format my console output shows for Addresses is

[
  { '12345678910': { ChannelType: 'SMS' } },
  { '12345678911': { ChannelType: 'SMS' } }
]

I'm using a map to call this

function createPhoneMessagingObject(phoneNumber: string) {
    return {
        [phoneNumber]: {
            ChannelType: 'SMS'
        }
    };
}

I tried wrapping key in array like in phone object, but per the output, the brackets goes away so maybe there's an easier/more correct way of doing this. I appreciate any help!

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