Node.js AWS Lambda function for creating thumbnails

index.js

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

const WIDTH = 200;
const S3 = new AWS.S3();

exports.handler = (event, context) => {
  event.Records.forEach((record, index, array) => {
    var bucket = record.s3.bucket.name;
    var key = record.s3.object.key;
    if(key.includes("thumbnail-")) return;
    var fileName = key.substr(key.lastIndexOf('/') + 1);
    var prefix = key.substring(0, key.lastIndexOf('/') + 1);
    var newKey = prefix + "thumbnail-" + fileName;
    console.log("bucket:", bucket, "key:", key, "fileName:", fileName, "newKey:", newKey);
    var resizeTransform = sharp().resize(WIDTH, undefined);
    S3.upload({
      Bucket: bucket,
      Key: newKey,
      Body:
        S3.getObject({
          Bucket: bucket, Key: key
        }).createReadStream().pipe(resizeTransform)
    }, function(err,data){
        if (err)
          context.fail(err)
        else
          context.succeed();
    });
  });
}