Lambda function that generated a pre-signed URL for uploading to S3

presignedUrl.js

const AWS = require('aws-sdk')
const s3 = new AWS.S3();

exports.handler = async (event) => {
  let folderName, fileName;
  try {
    folderName = event['queryStringParameters']['folder'];
    fileName = event['queryStringParameters']['name'];
  } catch(e) {
    return new Promise((reject) => {
      reject({
        "statusCode": 422,
        "headers": {
          "Access-Control-Allow-Origin": "*" 
        },
        "body": JSON.stringify({
          "message": "Need to specify name, folder param"})
      })
    })
  }
  
  return await getUploadURL(folderName, fileName);
};

const getUploadURL = async function(folderName, fileName) {
  const s3Params = {
    Bucket: 'budds',
    Key:  `${folderName}/${fileName}.jpg`,
    ACL: 'public-read',
    ContentType: 'application/x-www-form-urlencoded',
  };

  return new Promise((resolve, reject) => {
    let uploadURL = s3.getSignedUrl('putObject', s3Params)
    resolve({
      "statusCode": 200,
      "isBase64Encoded": false,
      "headers": {
        "Access-Control-Allow-Origin": "*"
      },
      "body": JSON.stringify({
          "uploadURL": uploadURL
      })
    })
  })
}