amazonS3 API to post and get media

server.js

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+const express = require('express');
+const multer  = require('multer');
+const AWS = require('aws-sdk');
+const fs=require('fs');
+require('dotenv').config();
+
+
+
+const app = express();
+
+// configuring the DiscStorage engine.
+const storage = multer.diskStorage({
+    destination : 'uploads/',
+    filename: function (req, file, cb) {
+      cb(null, file.originalname);
+    }
+});
+const upload = multer({ storage: storage });
+
+const downloaded = multer.diskStorage({
+  destination : 'downloads/',
+  filename: function (req, file, cb) {
+    cb(null, file.originalname);
+  }
+});
+const download = multer({ storage: downloaded });
+
+//setting the credentials
+//The region should be the region of the bucket that you created
+//Visit this if you have any confusion - https://docs.aws.amazon.com/general/latest/gr/rande.html
+AWS.config.update({
+    accessKeyId: process.env.S3_ACCESS_KEY,
+    secretAccessKey: process.env.S3_ACCESS_SECRET,
+    region: 'us-east-1',
+});
+
+//Creating a new instance of S3:
+const s3= new AWS.S3();
+
+//POST method route for uploading file
+app.post('/post_file', upload.single('demo_file'), function (req, res) {
+  //Multer middleware adds file(in case of single file ) or files(multiple files) object to the request object.
+  //req.file is the demo_file
+  uploadFile(req.file.path, req.file.filename ,res);
+})
+
+//GET method route for downloading/retrieving file
+app.get('/get_file/:file_name', (req,res)=>{
+  retrieveFile(req.params.file_name, res);
+});
+
+
+//listening to server 3000
+app.listen(3000,()=>{
+    console.log('Server running on port 3000');
+});
+
+//The uploadFile function
+function uploadFile(source,targetName,res){
+    console.log('preparing to upload...');
+    fs.readFileSync(source, function (err, filedata) {
+      if (!err) {
+        const putParams = {
+            Bucket      : process.env.S3_BUCKET_NAME,
+            Key         : targetName,
+            Body        : filedata
+        };
+        s3.putObject(putParams, function(err, data){
+          if (err) {
+            console.log('Could nor upload the file. Error :',err);
+            return res.send({success:false});
+          } 
+          else{
+            fs.unlink(source);// Deleting the file from uploads folder(Optional).Do Whatever you prefer.
+            console.log('Successfully uploaded the file');
+            return res.send({success:true});
+          }
+        });
+      }
+      else{
+        console.log({'err':err});
+      }
+    });
+}
+
+
+
+//The retrieveFile function
+function retrieveFile(filename,res){
+
+  const getParams = {
+    Bucket: process.env.S3_BUCKET_NAME,
+    Key: filename
+  };
+
+  s3.getObject(getParams, function(err, data) {
+    if (err){
+      return res.status(400).send({success:false,err:err});
+    }
+    else{
+      var buf = Buffer.from (data.Body)
+      fs.writeFileSync('downloads/image.jpg', buf)
+      return res.send(data.Body);
+    }
+  });
+}