Lambda snippet to upload file to S3

handler.js

'use strict';

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

// Set the Region 
AWS.config.update({
  accessKeyId: '***********',
  secretAccessKey: '*************',
  region: 'us-east-1',
  signatureVersion: 'v4'
});

// Create the S3 service object
const s3 = new AWS.S3();

module.exports.getPreSignedURLToPutToS3 = function(event, context, mainCallback) {
  // What does this function do?
  // 1. Receive the filename to be uploaded and Create a request param to make a request to create pre-signed URL to upload to S3
  // 2. Make the request to S3
  // 3. Get the pre-signed URL from S3
  // 4. Send the pre-signed URL from S3 as response

  // 1. Receive the filename to be uploaded and Create a request param to make a request to create pre-signed URL to upload to S3
  let requestObject = JSON.parse(event["body"]);

  const fileName = requestObject.fileName;
  const fileType = requestObject.fileType;
  const myBucket = 'jobobo-resumes';

  s3.getSignedUrl('putObject', {
    "Bucket": myBucket,
    "Key": fileName,
    "ContentType": fileType
  }, function (err, url) {
    if (err) {
      mainCallback(null, err);
    } else {
      mainCallback(null, url);    
    }
  });
};