s3.js

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

let secrets;
if (process.env.NODE_ENV == 'production') {
    secrets = process.env; // in prod the secrets are environment variables
} else {
    secrets = require('./secrets'); // in dev they are in secrets.json which is listed in .gitignore
}

//------passing credentials to AWS-----------------//

const s3 = new aws.S3({
    accessKeyId: secrets.AWS_KEY,
    secretAccessKey: secrets.AWS_SECRET
});

exports.upload = (req, res, next) => {
    const {file} = req;
    if(!file){
        console.log("Multer failed :(");
        return res.sendStatus(500);
    }

    const {filename, mimetype, size, path} = req.file;
    s3.putObject({
    Bucket: 'spicedling',
    ACL: 'public-read',
    Key: filename,
    Body: fs.createReadStream(path),
    ContentType: mimetype,
    ContentLength: size
}).promise().then(info => {
    console.log(info);
    next();
}).catch(err => {
    console.log('Error', err);
    res.sendStatus(500);
}).then(
    () => fs.unlink(path, () => {}));
};