index.js

const crypto = require('crypto');
const AWS = require("aws-sdk");
const config = {
    accessKeyId: process.env.AWS_ACCESS_KEY_ID,
    secretAccessKey: process.env.AWS_SECRET_ACCESS_KEY,
    bucketName: process.env.S3_BUCKET_NAME,
    region: process.env.AWS_DEFAULT_REGION
};
console.log(`accessKeyId = ${config.accessKeyId}`);
console.log(`secretAccessKey = ${config.secretAccessKey}`);
console.log(`bucketName = ${config.bucketName}`);
console.log(`region = ${config.region}`);

const s3 = new AWS.S3(config);

const getChecksum = (algorithm, data) => {
    return crypto.createHash(algorithm).update(data).digest('hex');
}

// Create content from string to stream
// To do: read data from DB then create a string
// let Readable = require("stream").Readable;
// let stream = new Readable();
// stream.push("number,first,last,handle\n"); 
// stream.push("1,Mark,Otto,@mdo\n"); 
// stream.push("2,Jacob,Thornton,@fat\n"); 
// stream.push("3,Larry,the Bird,@twitter\n"); 
// //stream.push("data,data,data"); // add data as a single string
// stream.push(null); // indicates end-of-file basically - the end of the stream

let s3ObjectName = "test/data.csv";

// // Upload content of stream to s3 
// let params = { Bucket: config.bucketName, Key: s3ObjectName, Body: stream };
// // Upload options: with concurrency of 1 and partSize of 10Mb
// // See https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/S3.html#upload-property
// let options = { partSize: 10 * 1024 * 1024, queueSize: 1 };
// // Use the promises version of the API
// // See https://docs.aws.amazon.com/sdk-for-javascript/v2/developer-guide/using-promises.html
// let upload = s3.upload(params, options).promise();
// upload.then(data => {
//     console.log(`Successfully uploaded ${s3ObjectName} to bucket`);
//     console.log(data);
// })
// .catch(err => {
//     console.log(err);
// });

// Setup read parameters
let readParams = { Bucket: config.bucketName, Key: s3ObjectName };

// Read object info and content from s3 
let getObject = s3.getObject(readParams).promise();
getObject.then(data => {
    console.log(`Successfully read ${s3ObjectName}`);
    console.log(data);

    console.log('*** Other Info ***');
    console.log(`Time now:     ${formatDate(new Date())}`);
    console.log(`LastModified: ${formatDate(data.LastModified)}`);
    console.log(`File size in bytes: ${data.ContentLength}`);
    let content = data.Body.toString('utf-8');
    console.log(`File content:\n${content}`);
    let algorithm = 'sha256';
    console.log(`${algorithm} hecksum: ${getChecksum(algorithm, content)}`)
})
.catch(err => {
    console.log(err);
});

const formatDate = (stringDate) => {
    let dt = new Date(stringDate);
    let year = dt.getFullYear();
    let month = ('0' + (dt.getMonth() + 1)).slice(-2);
    let date = ('0' + dt.getDate()).slice(-2);
    let hour = ('0' + dt.getHours()).slice(-2);
    let minute = ('0' + dt.getMinutes()).slice(-2);
    let seconds = ('0' + dt.getSeconds()).slice(-2);
    return year+month+date+hour+minute+seconds;
}

// Save to file to compare checksum with terminal command
// shasum -a 256 test.csv
var file = require('fs').createWriteStream(`${process.env.PWD}/test.csv`);
s3.getObject(readParams).createReadStream().pipe(file);