diff --git a/core/misc/drupal.js b/core/misc/drupal.js
index d509795b86..894d6dc782 100644
--- a/core/misc/drupal.js
+++ b/core/misc/drupal.js
@@ -1,583 +1 @@
-/**
- * @file
- * Defines the Drupal JavaScript API.
- */
-
-/**
- * A jQuery object, typically the return value from a `$(selector)` call.
- *
- * Holds an HTMLElement or a collection of HTMLElements.
- *
- * @typedef {object} jQuery
- *
- * @prop {number} length=0
- *   Number of elements contained in the jQuery object.
- */
-
-/**
- * Variable generated by Drupal that holds all translated strings from PHP.
- *
- * Content of this variable is automatically created by Drupal when using the
- * Interface Translation module. It holds the translation of strings used on
- * the page.
- *
- * This variable is used to pass data from the backend to the frontend. Data
- * contained in `drupalSettings` is used during behavior initialization.
- *
- * @global
- *
- * @var {object} drupalTranslations
- */
-
-/**
- * Global Drupal object.
- *
- * All Drupal JavaScript APIs are contained in this namespace.
- *
- * @global
- *
- * @namespace
- */
-window.Drupal = {behaviors: {}, locale: {}};
-
-// JavaScript should be made compatible with libraries other than jQuery by
-// wrapping it in an anonymous closure.
-(function (Drupal, drupalSettings, drupalTranslations) {
-
-  'use strict';
-
-  /**
-   * Helper to rethrow errors asynchronously.
-   *
-   * This way Errors bubbles up outside of the original callstack, making it
-   * easier to debug errors in the browser.
-   *
-   * @param {Error|string} error
-   *   The error to be thrown.
-   */
-  Drupal.throwError = function (error) {
-    setTimeout(function () { throw error; }, 0);
-  };
-
-  /**
-   * Custom error thrown after attach/detach if one or more behaviors failed.
-   * Initializes the JavaScript behaviors for page loads and Ajax requests.
-   *
-   * @callback Drupal~behaviorAttach
-   *
-   * @param {HTMLDocument|HTMLElement} context
-   *   An element to detach behaviors from.
-   * @param {?object} settings
-   *   An object containing settings for the current context. It is rarely used.
-   *
-   * @see Drupal.attachBehaviors
-   */
-
-  /**
-   * Reverts and cleans up JavaScript behavior initialization.
-   *
-   * @callback Drupal~behaviorDetach
-   *
-   * @param {HTMLDocument|HTMLElement} context
-   *   An element to attach behaviors to.
-   * @param {object} settings
-   *   An object containing settings for the current context.
-   * @param {string} trigger
-   *   One of `'unload'`, `'move'`, or `'serialize'`.
-   *
-   * @see Drupal.detachBehaviors
-   */
-
-  /**
-   * @typedef {object} Drupal~behavior
-   *
-   * @prop {Drupal~behaviorAttach} attach
-   *   Function run on page load and after an Ajax call.
-   * @prop {Drupal~behaviorDetach} detach
-   *   Function run when content is serialized or removed from the page.
-   */
-
-  /**
-   * Holds all initialization methods.
-   *
-   * @namespace Drupal.behaviors
-   *
-   * @type {Object.<string, Drupal~behavior>}
-   */
-
-  /**
-   * Defines a behavior to be run during attach and detach phases.
-   *
-   * Attaches all registered behaviors to a page element.
-   *
-   * Behaviors are event-triggered actions that attach to page elements,
-   * enhancing default non-JavaScript UIs. Behaviors are registered in the
-   * {@link Drupal.behaviors} object using the method 'attach' and optionally
-   * also 'detach'.
-   *
-   * {@link Drupal.attachBehaviors} is added below to the `jQuery.ready` event
-   * and therefore runs on initial page load. Developers implementing Ajax in
-   * their solutions should also call this function after new page content has
-   * been loaded, feeding in an element to be processed, in order to attach all
-   * behaviors to the new content.
-   *
-   * Behaviors should use `var elements =
-   * $(context).find(selector).once('behavior-name');` to ensure the behavior is
-   * attached only once to a given element. (Doing so enables the reprocessing
-   * of given elements, which may be needed on occasion despite the ability to
-   * limit behavior attachment to a particular element.)
-   *
-   * @example
-   * Drupal.behaviors.behaviorName = {
-   *   attach: function (context, settings) {
-   *     // ...
-   *   },
-   *   detach: function (context, settings, trigger) {
-   *     // ...
-   *   }
-   * };
-   *
-   * @param {HTMLDocument|HTMLElement} [context=document]
-   *   An element to attach behaviors to.
-   * @param {object} [settings=drupalSettings]
-   *   An object containing settings for the current context. If none is given,
-   *   the global {@link drupalSettings} object is used.
-   *
-   * @see Drupal~behaviorAttach
-   * @see Drupal.detachBehaviors
-   *
-   * @throws {Drupal~DrupalBehaviorError}
-   */
-  Drupal.attachBehaviors = function (context, settings) {
-    context = context || document;
-    settings = settings || drupalSettings;
-    var behaviors = Drupal.behaviors;
-    // Execute all of them.
-    for (var i in behaviors) {
-      if (behaviors.hasOwnProperty(i) && typeof behaviors[i].attach === 'function') {
-        // Don't stop the execution of behaviors in case of an error.
-        try {
-          behaviors[i].attach(context, settings);
-        }
-        catch (e) {
-          Drupal.throwError(e);
-        }
-      }
-    }
-  };
-
-  /**
-   * Detaches registered behaviors from a page element.
-   *
-   * Developers implementing Ajax in their solutions should call this function
-   * before page content is about to be removed, feeding in an element to be
-   * processed, in order to allow special behaviors to detach from the content.
-   *
-   * Such implementations should use `.findOnce()` and `.removeOnce()` to find
-   * elements with their corresponding `Drupal.behaviors.behaviorName.attach`
-   * implementation, i.e. `.removeOnce('behaviorName')`, to ensure the behavior
-   * is detached only from previously processed elements.
-   *
-   * @param {HTMLDocument|HTMLElement} [context=document]
-   *   An element to detach behaviors from.
-   * @param {object} [settings=drupalSettings]
-   *   An object containing settings for the current context. If none given,
-   *   the global {@link drupalSettings} object is used.
-   * @param {string} [trigger='unload']
-   *   A string containing what's causing the behaviors to be detached. The
-   *   possible triggers are:
-   *   - `'unload'`: The context element is being removed from the DOM.
-   *   - `'move'`: The element is about to be moved within the DOM (for example,
-   *     during a tabledrag row swap). After the move is completed,
-   *     {@link Drupal.attachBehaviors} is called, so that the behavior can undo
-   *     whatever it did in response to the move. Many behaviors won't need to
-   *     do anything simply in response to the element being moved, but because
-   *     IFRAME elements reload their "src" when being moved within the DOM,
-   *     behaviors bound to IFRAME elements (like WYSIWYG editors) may need to
-   *     take some action.
-   *   - `'serialize'`: When an Ajax form is submitted, this is called with the
-   *     form as the context. This provides every behavior within the form an
-   *     opportunity to ensure that the field elements have correct content
-   *     in them before the form is serialized. The canonical use-case is so
-   *     that WYSIWYG editors can update the hidden textarea to which they are
-   *     bound.
-   *
-   * @throws {Drupal~DrupalBehaviorError}
-   *
-   * @see Drupal~behaviorDetach
-   * @see Drupal.attachBehaviors
-   */
-  Drupal.detachBehaviors = function (context, settings, trigger) {
-    context = context || document;
-    settings = settings || drupalSettings;
-    trigger = trigger || 'unload';
-    var behaviors = Drupal.behaviors;
-    // Execute all of them.
-    for (var i in behaviors) {
-      if (behaviors.hasOwnProperty(i) && typeof behaviors[i].detach === 'function') {
-        // Don't stop the execution of behaviors in case of an error.
-        try {
-          behaviors[i].detach(context, settings, trigger);
-        }
-        catch (e) {
-          Drupal.throwError(e);
-        }
-      }
-    }
-  };
-
-  /**
-   * Encodes special characters in a plain-text string for display as HTML.
-   *
-   * @param {string} str
-   *   The string to be encoded.
-   *
-   * @return {string}
-   *   The encoded string.
-   *
-   * @ingroup sanitization
-   */
-  Drupal.checkPlain = function (str) {
-    str = str.toString()
-      .replace(/&/g, '&amp;')
-      .replace(/"/g, '&quot;')
-      .replace(/</g, '&lt;')
-      .replace(/>/g, '&gt;');
-    return str;
-  };
-
-  /**
-   * Replaces placeholders with sanitized values in a string.
-   *
-   * @param {string} str
-   *   A string with placeholders.
-   * @param {object} args
-   *   An object of replacements pairs to make. Incidences of any key in this
-   *   array are replaced with the corresponding value. Based on the first
-   *   character of the key, the value is escaped and/or themed:
-   *    - `'!variable'`: inserted as is.
-   *    - `'@variable'`: escape plain text to HTML ({@link Drupal.checkPlain}).
-   *    - `'%variable'`: escape text and theme as a placeholder for user-
-   *      submitted content ({@link Drupal.checkPlain} +
-   *      `{@link Drupal.theme}('placeholder')`).
-   *
-   * @return {string}
-   *   The formatted string.
-   *
-   * @see Drupal.t
-   */
-  Drupal.formatString = function (str, args) {
-    // Keep args intact.
-    var processedArgs = {};
-    // Transform arguments before inserting them.
-    for (var key in args) {
-      if (args.hasOwnProperty(key)) {
-        switch (key.charAt(0)) {
-          // Escaped only.
-          case '@':
-            processedArgs[key] = Drupal.checkPlain(args[key]);
-            break;
-
-          // Pass-through.
-          case '!':
-            processedArgs[key] = args[key];
-            break;
-
-          // Escaped and placeholder.
-          default:
-            processedArgs[key] = Drupal.theme('placeholder', args[key]);
-            break;
-        }
-      }
-    }
-
-    return Drupal.stringReplace(str, processedArgs, null);
-  };
-
-  /**
-   * Replaces substring.
-   *
-   * The longest keys will be tried first. Once a substring has been replaced,
-   * its new value will not be searched again.
-   *
-   * @param {string} str
-   *   A string with placeholders.
-   * @param {object} args
-   *   Key-value pairs.
-   * @param {Array|null} keys
-   *   Array of keys from `args`. Internal use only.
-   *
-   * @return {string}
-   *   The replaced string.
-   */
-  Drupal.stringReplace = function (str, args, keys) {
-    if (str.length === 0) {
-      return str;
-    }
-
-    // If the array of keys is not passed then collect the keys from the args.
-    if (!Array.isArray(keys)) {
-      keys = [];
-      for (var k in args) {
-        if (args.hasOwnProperty(k)) {
-          keys.push(k);
-        }
-      }
-
-      // Order the keys by the character length. The shortest one is the first.
-      keys.sort(function (a, b) { return a.length - b.length; });
-    }
-
-    if (keys.length === 0) {
-      return str;
-    }
-
-    // Take next longest one from the end.
-    var key = keys.pop();
-    var fragments = str.split(key);
-
-    if (keys.length) {
-      for (var i = 0; i < fragments.length; i++) {
-        // Process each fragment with a copy of remaining keys.
-        fragments[i] = Drupal.stringReplace(fragments[i], args, keys.slice(0));
-      }
-    }
-
-    return fragments.join(args[key]);
-  };
-
-  /**
-   * Translates strings to the page language, or a given language.
-   *
-   * See the documentation of the server-side t() function for further details.
-   *
-   * @param {string} str
-   *   A string containing the English text to translate.
-   * @param {Object.<string, string>} [args]
-   *   An object of replacements pairs to make after translation. Incidences
-   *   of any key in this array are replaced with the corresponding value.
-   *   See {@link Drupal.formatString}.
-   * @param {object} [options]
-   *   Additional options for translation.
-   * @param {string} [options.context='']
-   *   The context the source string belongs to.
-   *
-   * @return {string}
-   *   The formatted string.
-   *   The translated string.
-   */
-  Drupal.t = function (str, args, options) {
-    options = options || {};
-    options.context = options.context || '';
-
-    // Fetch the localized version of the string.
-    if (typeof drupalTranslations !== 'undefined' && drupalTranslations.strings && drupalTranslations.strings[options.context] && drupalTranslations.strings[options.context][str]) {
-      str = drupalTranslations.strings[options.context][str];
-    }
-
-    if (args) {
-      str = Drupal.formatString(str, args);
-    }
-    return str;
-  };
-
-  /**
-   * Returns the URL to a Drupal page.
-   *
-   * @param {string} path
-   *   Drupal path to transform to URL.
-   *
-   * @return {string}
-   *   The full URL.
-   */
-  Drupal.url = function (path) {
-    return drupalSettings.path.baseUrl + drupalSettings.path.pathPrefix + path;
-  };
-
-  /**
-   * Returns the passed in URL as an absolute URL.
-   *
-   * @param {string} url
-   *   The URL string to be normalized to an absolute URL.
-   *
-   * @return {string}
-   *   The normalized, absolute URL.
-   *
-   * @see https://github.com/angular/angular.js/blob/v1.4.4/src/ng/urlUtils.js
-   * @see https://grack.com/blog/2009/11/17/absolutizing-url-in-javascript
-   * @see https://github.com/jquery/jquery-ui/blob/1.11.4/ui/tabs.js#L53
-   */
-  Drupal.url.toAbsolute = function (url) {
-    var urlParsingNode = document.createElement('a');
-
-    // Decode the URL first; this is required by IE <= 6. Decoding non-UTF-8
-    // strings may throw an exception.
-    try {
-      url = decodeURIComponent(url);
-    }
-    catch (e) {
-      // Empty.
-    }
-
-    urlParsingNode.setAttribute('href', url);
-
-    // IE <= 7 normalizes the URL when assigned to the anchor node similar to
-    // the other browsers.
-    return urlParsingNode.cloneNode(false).href;
-  };
-
-  /**
-   * Returns true if the URL is within Drupal's base path.
-   *
-   * @param {string} url
-   *   The URL string to be tested.
-   *
-   * @return {bool}
-   *   `true` if local.
-   *
-   * @see https://github.com/jquery/jquery-ui/blob/1.11.4/ui/tabs.js#L58
-   */
-  Drupal.url.isLocal = function (url) {
-    // Always use browser-derived absolute URLs in the comparison, to avoid
-    // attempts to break out of the base path using directory traversal.
-    var absoluteUrl = Drupal.url.toAbsolute(url);
-    var protocol = location.protocol;
-
-    // Consider URLs that match this site's base URL but use HTTPS instead of HTTP
-    // as local as well.
-    if (protocol === 'http:' && absoluteUrl.indexOf('https:') === 0) {
-      protocol = 'https:';
-    }
-    var baseUrl = protocol + '//' + location.host + drupalSettings.path.baseUrl.slice(0, -1);
-
-    // Decoding non-UTF-8 strings may throw an exception.
-    try {
-      absoluteUrl = decodeURIComponent(absoluteUrl);
-    }
-    catch (e) {
-      // Empty.
-    }
-    try {
-      baseUrl = decodeURIComponent(baseUrl);
-    }
-    catch (e) {
-      // Empty.
-    }
-
-    // The given URL matches the site's base URL, or has a path under the site's
-    // base URL.
-    return absoluteUrl === baseUrl || absoluteUrl.indexOf(baseUrl + '/') === 0;
-  };
-
-  /**
-   * Formats a string containing a count of items.
-   *
-   * This function ensures that the string is pluralized correctly. Since
-   * {@link Drupal.t} is called by this function, make sure not to pass
-   * already-localized strings to it.
-   *
-   * See the documentation of the server-side
-   * \Drupal\Core\StringTranslation\TranslationInterface::formatPlural()
-   * function for more details.
-   *
-   * @param {number} count
-   *   The item count to display.
-   * @param {string} singular
-   *   The string for the singular case. Please make sure it is clear this is
-   *   singular, to ease translation (e.g. use "1 new comment" instead of "1
-   *   new"). Do not use @count in the singular string.
-   * @param {string} plural
-   *   The string for the plural case. Please make sure it is clear this is
-   *   plural, to ease translation. Use @count in place of the item count, as in
-   *   "@count new comments".
-   * @param {object} [args]
-   *   An object of replacements pairs to make after translation. Incidences
-   *   of any key in this array are replaced with the corresponding value.
-   *   See {@link Drupal.formatString}.
-   *   Note that you do not need to include @count in this array.
-   *   This replacement is done automatically for the plural case.
-   * @param {object} [options]
-   *   The options to pass to the {@link Drupal.t} function.
-   *
-   * @return {string}
-   *   A translated string.
-   */
-  Drupal.formatPlural = function (count, singular, plural, args, options) {
-    args = args || {};
-    args['@count'] = count;
-
-    var pluralDelimiter = drupalSettings.pluralDelimiter;
-    var translations = Drupal.t(singular + pluralDelimiter + plural, args, options).split(pluralDelimiter);
-    var index = 0;
-
-    // Determine the index of the plural form.
-    if (typeof drupalTranslations !== 'undefined' && drupalTranslations.pluralFormula) {
-      index = count in drupalTranslations.pluralFormula ? drupalTranslations.pluralFormula[count] : drupalTranslations.pluralFormula['default'];
-    }
-    else if (args['@count'] !== 1) {
-      index = 1;
-    }
-
-    return translations[index];
-  };
-
-  /**
-   * Encodes a Drupal path for use in a URL.
-   *
-   * For aesthetic reasons slashes are not escaped.
-   *
-   * @param {string} item
-   *   Unencoded path.
-   *
-   * @return {string}
-   *   The encoded path.
-   */
-  Drupal.encodePath = function (item) {
-    return window.encodeURIComponent(item).replace(/%2F/g, '/');
-  };
-
-  /**
-   * Generates the themed representation of a Drupal object.
-   *
-   * All requests for themed output must go through this function. It examines
-   * the request and routes it to the appropriate theme function. If the current
-   * theme does not provide an override function, the generic theme function is
-   * called.
-   *
-   * @example
-   * <caption>To retrieve the HTML for text that should be emphasized and
-   * displayed as a placeholder inside a sentence.</caption>
-   * Drupal.theme('placeholder', text);
-   *
-   * @namespace
-   *
-   * @param {function} func
-   *   The name of the theme function to call.
-   * @param {...args}
-   *   Additional arguments to pass along to the theme function.
-   *
-   * @return {string|object|HTMLElement|jQuery}
-   *   Any data the theme function returns. This could be a plain HTML string,
-   *   but also a complex object.
-   */
-  Drupal.theme = function (func) {
-    var args = Array.prototype.slice.apply(arguments, [1]);
-    if (func in Drupal.theme) {
-      return Drupal.theme[func].apply(this, args);
-    }
-  };
-
-  /**
-   * Formats text for emphasized display in a placeholder inside a sentence.
-   *
-   * @param {string} str
-   *   The text to format (plain-text).
-   *
-   * @return {string}
-   *   The formatted text (html).
-   */
-  Drupal.theme.placeholder = function (str) {
-    return '<em class="placeholder">' + Drupal.checkPlain(str) + '</em>';
-  };
-
-})(Drupal, window.drupalSettings, window.drupalTranslations);
+window.Drupal={behaviors:{},locale:{}},function(c,d,f){c.throwError=function(g){setTimeout(function(){throw g},0)},c.attachBehaviors=function(g,h){g=g||document,h=h||d;var j=c.behaviors;for(var l in j)if(j.hasOwnProperty(l)&&'function'==typeof j[l].attach)try{j[l].attach(g,h)}catch(m){c.throwError(m)}},c.detachBehaviors=function(g,h,j){g=g||document,h=h||d,j=j||'unload';var l=c.behaviors;for(var m in l)if(l.hasOwnProperty(m)&&'function'==typeof l[m].detach)try{l[m].detach(g,h,j)}catch(n){c.throwError(n)}},c.checkPlain=function(g){return g=g.toString().replace(/&/g,'&amp;').replace(/"/g,'&quot;').replace(/</g,'&lt;').replace(/>/g,'&gt;'),g},c.formatString=function(g,h){var j={};for(var l in h)if(h.hasOwnProperty(l))switch(l.charAt(0)){case'@':j[l]=c.checkPlain(h[l]);break;case'!':j[l]=h[l];break;default:j[l]=c.theme('placeholder',h[l]);}return c.stringReplace(g,j,null)},c.stringReplace=function(g,h,j){if(0===g.length)return g;if(!Array.isArray(j)){for(var n in j=[],h)h.hasOwnProperty(n)&&j.push(n);j.sort(function(n,o){return n.length-o.length})}if(0===j.length)return g;var l=j.pop(),m=g.split(l);if(j.length)for(var n=0;n<m.length;n++)m[n]=c.stringReplace(m[n],h,j.slice(0));return m.join(h[l])},c.t=function(g,h,j){return j=j||{},j.context=j.context||'','undefined'!=typeof f&&f.strings&&f.strings[j.context]&&f.strings[j.context][g]&&(g=f.strings[j.context][g]),h&&(g=c.formatString(g,h)),g},c.url=function(g){return d.path.baseUrl+d.path.pathPrefix+g},c.url.toAbsolute=function(g){var h=document.createElement('a');try{g=decodeURIComponent(g)}catch(j){}return h.setAttribute('href',g),h.cloneNode(!1).href},c.url.isLocal=function(g){var h=c.url.toAbsolute(g),j=location.protocol;'http:'===j&&0===h.indexOf('https:')&&(j='https:');var l=j+'//'+location.host+d.path.baseUrl.slice(0,-1);try{h=decodeURIComponent(h)}catch(m){}try{l=decodeURIComponent(l)}catch(m){}return h===l||0===h.indexOf(l+'/')},c.formatPlural=function(g,h,j,l,m){l=l||{},l['@count']=g;var n=d.pluralDelimiter,o=c.t(h+n+j,l,m).split(n),p=0;return'undefined'!=typeof f&&f.pluralFormula?p=g in f.pluralFormula?f.pluralFormula[g]:f.pluralFormula['default']:1!==l['@count']&&(p=1),o[p]},c.encodePath=function(g){return window.encodeURIComponent(g).replace(/%2F/g,'/')},c.theme=function(g){var h=Array.prototype.slice.apply(arguments,[1]);if(g in c.theme)return c.theme[g].apply(this,h)},c.theme.placeholder=function(g){return'<em class="placeholder">'+c.checkPlain(g)+'</em>'}}(Drupal,window.drupalSettings,window.drupalTranslations);
\ No newline at end of file
diff --git a/core/package.json b/core/package.json
index b20516db94..aa4d06ba1d 100644
--- a/core/package.json
+++ b/core/package.json
@@ -4,15 +4,16 @@
   "license": "GPL-2.0",
   "private": true,
   "scripts": {
-    "build:js": "node ./scripts/js/babel-es6-build.js",
+    "build:js": "BABEL_ENV=production node ./scripts/js/babel-es6-build.js",
     "watch:js": "node ./scripts/js/babel-es6-watch.js",
     "lint:core-js": "node ./node_modules/eslint/bin/eslint.js --ext=.es6.js . --fix || exit 0"
   },
   "devDependencies": {
-    "babel-core": "6.24.0",
-    "babel-preset-es2015": "6.16.0",
+    "babel-core": "^6.24.1",
+    "babel-preset-babili": "0.0.12",
+    "babel-preset-env": "1.4.0",
     "chokidar": "1.6.1",
-    "eslint": "3.18.0",
+    "eslint": "3.19.0",
     "eslint-config-airbnb": "14.1.0",
     "eslint-plugin-import": "2.2.0",
     "eslint-plugin-jsx-a11y": "4.0.0",
@@ -21,7 +22,25 @@
   },
   "babel": {
     "presets": [
-      "es2015"
-    ]
+      [
+        "env",
+        {
+          "modules": false,
+          "targets": {
+            "browsers": [
+              "last 2 versions",
+              "ie >= 11"
+            ]
+          }
+        }
+      ]
+    ],
+    "env": {
+      "production": {
+        "presets": [
+          "babili"
+        ]
+      }
+    }
   }
 }
diff --git a/core/scripts/js/babel-es6-build.js b/core/scripts/js/babel-es6-build.js
index e073f6a431..589f64d5e3 100644
--- a/core/scripts/js/babel-es6-build.js
+++ b/core/scripts/js/babel-es6-build.js
@@ -11,44 +11,23 @@
 
 const fs = require('fs');
 const path = require('path');
-const babel = require('babel-core');
 const glob = require('glob');
 
-// Logging human-readable timestamp.
-const log = function (message) {
-  // eslint-disable-next-line no-console
-  console.log(`[${new Date().toTimeString().slice(0, 8)}] ${message}`);
-};
-
-function addSourceMappingUrl(code, loc) {
-  return code + '\n\n//# sourceMappingURL=' + path.basename(loc);
-}
-
-const changedOrAdded = (filePath) => {
-  babel.transformFile(filePath, {
-    sourceMaps: true,
-    comments: false
-  }, function (err, result) {
-    const fileName = filePath.slice(0, -7);
-    // we've requested for a sourcemap to be written to disk
-    let mapLoc = `${fileName}.js.map`;
-
-    fs.writeFile(mapLoc, JSON.stringify(result.map));
-    fs.writeFile(`${fileName}.js`, addSourceMappingUrl(result.code, mapLoc));
-
-    log(`'${filePath}' is being processed.`);
-  });
-};
+const changeOrAdded = require('./changeOrAdded');
+const log = require('./log');
 
+// Match only on .es6.js files.
 const fileMatch = './**/*.es6.js';
+// Ignore everything in node_modules
 const globOptions = {
-  ignore: 'node_modules/**'
+  ignore: './node_modules/**'
 };
 const processFiles = (error, filePaths) => {
   if (error) {
     process.exitCode = 1;
   }
-  filePaths.forEach(changedOrAdded);
+  // Process all the found files.
+  filePaths.forEach(changeOrAdded);
 };
 glob(fileMatch, globOptions, processFiles);
 process.exitCode = 0;
diff --git a/core/scripts/js/babel-es6-watch.js b/core/scripts/js/babel-es6-watch.js
index d614774f29..9b49482236 100644
--- a/core/scripts/js/babel-es6-watch.js
+++ b/core/scripts/js/babel-es6-watch.js
@@ -11,50 +11,29 @@
 
 const fs = require('fs');
 const path = require('path');
-const babel = require('babel-core');
 const chokidar = require('chokidar');
 
-// Logging human-readable timestamp.
-const log = function log(message) {
-  // eslint-disable-next-line no-console
-  console.log(`[${new Date().toTimeString().slice(0, 8)}] ${message}`);
-};
-
-function addSourceMappingUrl(code, loc) {
-  return `${code}\n\n//# sourceMappingURL=${path.basename(loc)}`;
-}
+const changeOrAdded = require('./changeOrAdded');
+const log = require('./log');
 
+// Match only on .es6.js files.
 const fileMatch = './**/*.es6.js';
+// Ignore everything in node_modules
 const watcher = chokidar.watch(fileMatch, {
   ignoreInitial: true,
-  ignored: 'node_modules/**'
+  ignored: './node_modules/**'
 });
 
-const changedOrAdded = (filePath) => {
-  babel.transformFile(filePath, {
-    sourceMaps: true,
-    comments: false
-  }, (err, result) => {
-    const fileName = filePath.slice(0, -7);
-    // we've requested for a sourcemap to be written to disk
-    const mapLoc = `${fileName}.js.map`;
-
-    fs.writeFileSync(mapLoc, JSON.stringify(result.map));
-    fs.writeFileSync(`${fileName}.js`, addSourceMappingUrl(result.code, mapLoc));
-
-    log(`'${filePath}' has been changed.`);
-  });
-};
-
 const unlinkHandler = (err) => {
   if (err) {
     log(err);
   }
 };
 
+// Watch for filesystem changes.
 watcher
-  .on('add', filePath => changedOrAdded(filePath))
-  .on('change', filePath => changedOrAdded(filePath))
+  .on('add', changeOrAdded)
+  .on('change', changeOrAdded)
   .on('unlink', (filePath) => {
     const fileName = filePath.slice(0, -7);
     fs.stat(`${fileName}.js`, () => {
diff --git a/core/scripts/js/changeOrAdded.js b/core/scripts/js/changeOrAdded.js
new file mode 100644
index 0000000000..0938b108d8
--- /dev/null
+++ b/core/scripts/js/changeOrAdded.js
@@ -0,0 +1,25 @@
+const fs = require('fs');
+const babel = require('babel-core');
+
+const log = require('./log');
+
+module.exports = (filePath) => {
+  const moduleName = filePath.slice(0, -7);
+  log(`'${filePath}' is being processed.`);
+  // Transform the file.
+  // Check process.env.BABEL_ENV to see if we should create sourcemaps.
+  babel.transformFile(
+    filePath,
+    {
+      sourceMaps: process.env.BABEL_ENV ? false : 'inline',
+      comments: false
+    },
+    (err, result) => {
+      const fileName = filePath.slice(0, -7);
+      // Write the result to the filesystem.
+      fs.writeFile(`${fileName}.js`, result.code, () => {
+        log(`'${filePath}' is finished.`);
+      });
+    }
+  );
+}
diff --git a/core/scripts/js/log.js b/core/scripts/js/log.js
new file mode 100644
index 0000000000..08349b3ae3
--- /dev/null
+++ b/core/scripts/js/log.js
@@ -0,0 +1,4 @@
+module.exports = (message) => {
+  // Logging human-readable timestamp.
+  console.log(`[${new Date().toTimeString().slice(0, 8)}] ${message}`);
+}
