index.js

'use strict';

let AWS = require('aws-sdk');
let s3 = new AWS.S3({apiVersion: '2006-03-01'});
let Rx =  require('rx');
let AdmZip = require('adm-zip');
let bucket = 'my-bucket';

exports.handler = (event, context, callback) => {
  let file_key = decodeURIComponent(event.Records[0].s3.object.key.replace(/\+/g, ' '));
  let params = { Bucket: bucket, Key: file_key };
  s3.getObject(params, (err, data) => {
    if (err) {
      callback(err, null);
    } else {
      if (!data) callback(null, 'No Data!');
      let zip = new AdmZip(data.Body);
      let zipEntries = zip.getEntries(); // ZipEntry objects
      let source = Rx.Observable.from(zipEntries);
      let results = [];

      source.subscribe(
        (zipEntry) => {
          let params = {
            Bucket  : bucket,
            Key     : zipEntry.name,
            Body    : zipEntry.getCompressedData() // decompressed file as buffer
          };
          // upload decompressed file
          s3.putObject(params, (err, data) => {
            if (err) console.log(err, err.stack); // an error occurred
            else results.push(data);           // successful response
          });
        },
        (err) => {
          callback(err, null);
        },
        () => {
          let params = { Bucket: bucket, Key: file_key };
          // Delete zip file
          s3.deleteObject(params, (err, data) => {
            if (err) {
              callback(err, null);
            } else {
              callback(null, data);
            }
          });
        }
      );
    }
  });
};