var AWS = require('aws-sdk');

const s3bucket = process.env.BUCKET
var s3 = new AWS.S3({params: {Bucket: s3bucket}});

function getS3ObjectPromise = (key) => {
    var params = {Bucket: s3bucket, Key: key + '.json'};
    return new Promise((resolve, reject) => {
        s3.getObject(params).promise()
        .then((result) => {
            // read s3Object as string
            resolve(result.Body.toString());
        })
        .catch((err) => {
            console.log('getS3ObjectPromise.err ' + err.message);
            reject({'error': err});
        });
    });
}

getS3ObjectPromise('<s3objectKey>').then((data) => {
  console.log('data received for key');
  console.log(data);
}).catch((err) => {
  console.log('ups, something went wrong');
  console.log(err)
});