index.js

require('dotenv/config')
const express = require('express')
const multer = require('multer')
const AWS = require('aws-sdk')
const uuid = require('uuid').v4;
const app = express()
const port = process.env.PORT || 3000

const s3 = (process.env.NODE_ENV == "development") ? 
    new AWS.S3({
        credentials: {
            accessKeyId: process.env.AWS_ACCESS_KEY,
            secretAccessKey: process.env.AWS_SECRET_ACCESS_KEY,
        },
    })
    :
    new AWS.S3()

const storage = multer.memoryStorage({
    destination: function(req, file, callback) {
        callback(null, '')
    }
})

const upload = multer({storage}).single('image')

app.set('view engine', 'ejs');

app.get('/', (req, res) => {
    res.render('index');
});

app.post('/upload',upload,(req, res) => {

    let myFile = req.file.originalname.split(".")
    const fileType = myFile[myFile.length - 1]

    const params = {
        Bucket: process.env.AWS_BUCKET_NAME,
        Key: `${uuid()}.${fileType}`,
        Body: req.file.buffer
    }

    s3.upload(params, (error, data) => {
        if(error){
            res.status(500).send(error)
        }

        res.status(200).send(data)
    })

    var presignedGETURL = s3.getSignedUrl('getObject', {
        Bucket: process.env.AWS_BUCKET_NAME,
        Key: `${uuid()}.${fileType}`,
        Expires: 1000*5 //time to expire in seconds
    });
    console.log(presignedGETURL, " presignedGETURL");
})

app.listen(port, () => {
    console.log(`Server is up at ${port}`)
})