S3 download promise: nodeJS promise to download file from amazon S3 to local destination

s3download_promise.js

const AWS = require('aws-sdk');
const fs = require('fs')

const s3download = (bucketName, keyName, localDest) => {

    if (typeof localDest == 'undefined') {
        localDest = keyName;
    }

    let params = {
        Bucket: bucketName,
        Key: keyName
    }

    let file = fs.createWriteStream(localDest)

    return new Promise((resolve, reject) => {
        s3.getObject(params).createReadStream()
        .on('end', () => {
            return resolve();
        })
        .on('error', (error) => {
            return reject(error);
        }).pipe(file)
    });
};

Same code but did some minor cleanups and adds missing import. @milesrichardson

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

var s3 = new AWS.S3();

const s3download = (bucketName, keyName, localDest) => {

    if (typeof localDest == 'undefined') {
        localDest = keyName;
    }

    let params = {
        Bucket: bucketName,
        Key: keyName
    };

    let file = fs.createWriteStream(localDest);

    return new Promise((resolve, reject) => {
        s3.getObject(params).createReadStream()
        .on('end', () => {
            return resolve();
        })
        .on('error', (error) => {
            return reject(error);
        }).pipe(file);
    });
};

Great solutiion

I think this the solution from @steima is the correct implementation, as for me I was using the 1st solution where the end event came but does not mean the files were written, my next step which reads the files out, turns to be an incomplete file.

Same code but did some minor cleanups and adds missing import. @milesrichardson

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

var s3 = new AWS.S3();

const s3download = (bucketName, keyName, localDest) => {

    if (typeof localDest == 'undefined') {
        localDest = keyName;
    }

    let params = {
        Bucket: bucketName,
        Key: keyName
    };

    let file = fs.createWriteStream(localDest);

    return new Promise((resolve, reject) => {
        s3.getObject(params).createReadStream()
        .on('end', () => {
            return resolve();
        })
        .on('error', (error) => {
            return reject(error);
        }).pipe(file);
    });
};

A naive question: Why the resolve and reject is on read stream but not write stream? Thanks!