Lambda - Query DynamoDB items between ISO dates

dynamodb_query.js

const AWS = require('aws-sdk');
const REGION = 'us-east-1';
const DYNAMODB = new AWS.DynamoDB.DocumentClient();
const TABLE = "ttn-events";

exports.handler = async(event) => {
    var date = new Date();
    //dates should be obtained from request
    var end = date.toISOString();
    var start = new Date(date.setDate(date.getDate()-7)).toISOString();
    let params = {
        TableName: TABLE,
        ProjectionExpression:"#dvc, #tm, decoded_payload",
        KeyConditionExpression: "#dvc = :deviceId and #tm between :start and :end",
        ExpressionAttributeNames: {
            "#dvc": "device",
            "#tm": "time"
        },
        ExpressionAttributeValues: {
            ":deviceId": event.pathParameters.id,
            ":start": start,
            ":end": end
        }
    };

    let results = await DYNAMODB.query(params).promise();

    if (results.Items) {
        var data = [];
        results.Items.map(async(event, i) => {
            const payload = JSON.parse(event.decoded_payload);
            let obj = {
                "device": event.device,
                "time": event.time,
                ...payload
            };
            data.push(obj);
        });
        // return data;
        let response = {
            statusCode: 200,
            body: JSON.stringify(data),
        };
        return response;
    }
    else {
        let response = {
            statusCode: 500,
            body: JSON.stringify(results),
        };
        return response;
    }
};