diff --git a/browser/base/content/test/general/browser.ini b/browser/base/content/test/general/browser.ini
index 38949cc6d46..a02a166c0eb 100644
--- a/browser/base/content/test/general/browser.ini
+++ b/browser/base/content/test/general/browser.ini
@@ -64,6 +64,7 @@ support-files =
   offlineQuotaNotification.cacheManifest
   offlineQuotaNotification.html
   page_style_sample.html
+  parsingTestHelpers.jsm
   print_postdata.sjs
   redirect_bug623155.sjs
   searchSuggestionEngine.sjs
@@ -342,6 +343,7 @@ skip-if = buildapp == 'mulet' || e10s # Bug 866413 - PageInfo doesn't work in e1
 skip-if = e10s # Bug ?????? - test directly manipulates content
 
 [browser_parsable_css.js]
+[browser_parsable_script.js]
 
 [browser_pinnedTabs.js]
 skip-if = e10s # Bug 921905 - pinTab/unpinTab fail in e10s
diff --git a/browser/base/content/test/general/browser_parsable_css.js b/browser/base/content/test/general/browser_parsable_css.js
index b366a7d4599..57393535d13 100644
--- a/browser/base/content/test/general/browser_parsable_css.js
+++ b/browser/base/content/test/general/browser_parsable_css.js
@@ -17,6 +17,9 @@ const kWhitelist = [
   {sourceName: /loop\/.*sdk-content\/.*\.css$/i /* TokBox SDK assets, see bug 1032469 */}
 ];
 
+let moduleLocation = gTestPath.replace(/\/[^\/]*$/i, "/parsingTestHelpers.jsm");
+let {generateURIsFromDirTree} = Cu.import(moduleLocation, {});
+
 /**
  * Check if an error should be ignored due to matching one of the whitelist
  * objects defined in kWhitelist
@@ -40,113 +43,12 @@ function ignoredError(aErrorObject) {
   return false;
 }
 
-
-/**
- * Returns a promise that is resolved with a list of CSS files to check,
- * represented by their nsIURI objects.
- *
- * @param appDir the application directory to scan for CSS files (nsIFile)
- */
-function generateURIsFromDirTree(appDir) {
-  let rv = [];
-  let dirQueue = [appDir.path];
-  return Task.spawn(function*() {
-    while (dirQueue.length) {
-      let nextDir = dirQueue.shift();
-      let {subdirs, cssfiles} = yield iterateOverPath(nextDir);
-      dirQueue = dirQueue.concat(subdirs);
-      rv = rv.concat(cssfiles);
-    }
-    return rv;
-  });
-}
-
-/* Shorthand constructor to construct an nsI(Local)File */
-let LocalFile = Components.Constructor("@mozilla.org/file/local;1", Ci.nsIFile, "initWithPath");
-
-/**
- * Uses OS.File.DirectoryIterator to asynchronously iterate over a directory.
- * It returns a promise that is resolved with an object with two properties:
- *  - cssfiles: an array of nsIURIs corresponding to CSS that needs checking
- *  - subdirs: an array of paths for subdirectories we need to recurse into
- *             (handled by generateURIsFromDirTree above)
- *
- * @param path the path to check (string)
- */
-function iterateOverPath(path) {
-  let iterator = new OS.File.DirectoryIterator(path);
-  let parentDir = new LocalFile(path);
-  let subdirs = [];
-  let cssfiles = [];
-  // Iterate through the directory
-  let promise = iterator.forEach(
-    function onEntry(entry) {
-      if (entry.isDir) {
-        let subdir = parentDir.clone();
-        subdir.append(entry.name);
-        subdirs.push(subdir.path);
-      } else if (entry.name.endsWith(".css")) {
-        let file = parentDir.clone();
-        file.append(entry.name);
-        let uriSpec = getURLForFile(file);
-        cssfiles.push(Services.io.newURI(uriSpec, null, null));
-      } else if (entry.name.endsWith(".ja")) {
-        let file = parentDir.clone();
-        file.append(entry.name);
-        let subentries = [uri for (uri of generateEntriesFromJarFile(file))];
-        cssfiles = cssfiles.concat(subentries);
-      }
-    }
-  );
-
-  let outerPromise = Promise.defer();
-  promise.then(function() {
-    outerPromise.resolve({cssfiles: cssfiles, subdirs: subdirs});
-    iterator.close();
-  }, function(e) {
-    outerPromise.reject(e);
-    iterator.close();
-  });
-  return outerPromise.promise;
-}
-
-/* Helper function to generate a URI spec (NB: not an nsIURI yet!)
- * given an nsIFile object */
-function getURLForFile(file) {
-  let fileHandler = Services.io.getProtocolHandler("file");
-  fileHandler = fileHandler.QueryInterface(Ci.nsIFileProtocolHandler);
-  return fileHandler.getURLSpecFromFile(file);
-}
-
-/**
- * A generator that generates nsIURIs for CSS files found in jar files
- * like omni.ja.
- *
- * @param jarFile an nsIFile object for the jar file that needs checking.
- */
-function* generateEntriesFromJarFile(jarFile) {
-  const ZipReader = new Components.Constructor("@mozilla.org/libjar/zip-reader;1", "nsIZipReader", "open");
-  let zr = new ZipReader(jarFile);
-  let entryEnumerator = zr.findEntries("*.css$");
-
-  const kURIStart = getURLForFile(jarFile);
-  while (entryEnumerator.hasMore()) {
-    let entry = entryEnumerator.getNext();
-    let entryURISpec = "jar:" + kURIStart + "!/" + entry;
-    yield Services.io.newURI(entryURISpec, null, null);
-  }
-  zr.close();
-}
-
-/**
- * The actual test.
- */
 add_task(function checkAllTheCSS() {
   let appDir = Services.dirsvc.get("XCurProcD", Ci.nsIFile);
   // This asynchronously produces a list of URLs (sadly, mostly sync on our
   // test infrastructure because it runs against jarfiles there, and
   // our zipreader APIs are all sync)
-  let uris = yield generateURIsFromDirTree(appDir);
+  let uris = yield generateURIsFromDirTree(appDir, ".css");
 
   // Create a clean iframe to load all the files into:
   let hiddenWin = Services.appShell.hiddenDOMWindow;
diff --git a/browser/base/content/test/general/browser_parsable_script.js b/browser/base/content/test/general/browser_parsable_script.js
new file mode 100644
index 00000000000..01e907172d4
--- /dev/null
+++ b/browser/base/content/test/general/browser_parsable_script.js
@@ -0,0 +1,83 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/* This list allows pre-existing or 'unfixable' JS issues to remain, while we
+ * detect newly occurring issues in shipping JS. It is a list of regexes
+ * matching files which have errors:
+ */
+const kWhitelist = new Set([
+  /defaults\/profile\/prefs.js$/,
+]);
+
+
+let moduleLocation = gTestPath.replace(/\/[^\/]*$/i, "/parsingTestHelpers.jsm");
+let {generateURIsFromDirTree} = Cu.import(moduleLocation, {});
+let {Reflect} = Cu.import("resource://gre/modules/reflect.jsm", {});
+
+/**
+ * Check if an error should be ignored due to matching one of the whitelist
+ * objects defined in kWhitelist
+ *
+ * @param uri the uri to check against the whitelist
+ * @return true if the uri should be skipped, false otherwise.
+ */
+function uriIsWhiteListed(uri) {
+  for (let whitelistItem of kWhitelist) {
+    if (whitelistItem.test(uri.spec)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+function parsePromise(uri) {
+  let promise = new Promise((resolve, reject) => {
+    let xhr = new XMLHttpRequest();
+    xhr.open("GET", uri, true);
+    xhr.onreadystatechange = function() {
+      if (this.readyState == this.DONE) {
+        let scriptText = this.responseText;
+        let ast;
+        try {
+          info("Checking " + uri);
+          ast = Reflect.parse(scriptText);
+          resolve(true);
+        } catch (ex) {
+          let errorMsg = "Script error reading " + uri + ": " + ex;
+          ok(false, errorMsg);
+          resolve(false);
+        }
+      }
+    };
+    xhr.onerror = (error) => {
+      ok(false, "XHR error reading " + uri + ": " + error);
+      resolve(false);
+    };
+    xhr.overrideMimeType("application/javascript");
+    xhr.send(null);
+  });
+  return promise;
+}
+
+add_task(function* checkAllTheJS() {
+  let appDir = Services.dirsvc.get("XCurProcD", Ci.nsIFile);
+  // This asynchronously produces a list of URLs (sadly, mostly sync on our
+  // test infrastructure because it runs against jarfiles there, and
+  // our zipreader APIs are all sync)
+  let uris = yield generateURIsFromDirTree(appDir, [".js", ".jsm"]);
+
+  // We create an array of promises so we can parallelize all our parsing
+  // and file loading activity:
+  let allPromises = [];
+  for (let uri of uris) {
+    if (uriIsWhiteListed(uri)) {
+      info("Not checking " + uri.spec);
+      continue;
+    }
+    allPromises.push(parsePromise(uri.spec));
+  }
+
+  let promiseResults = yield Promise.all(allPromises);
+  is(promiseResults.filter((x) => !x).length, 0, "There should be 0 parsing errors");
+});
+
diff --git a/browser/base/content/test/general/parsingTestHelpers.jsm b/browser/base/content/test/general/parsingTestHelpers.jsm
new file mode 100644
index 00000000000..04a095bd7e4
--- /dev/null
+++ b/browser/base/content/test/general/parsingTestHelpers.jsm
@@ -0,0 +1,126 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+this.EXPORTED_SYMBOLS = ["generateURIsFromDirTree"];
+
+const {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;
+
+/* Shorthand constructors to construct an nsI(Local)File and zip reader: */
+const LocalFile = new Components.Constructor("@mozilla.org/file/local;1", Ci.nsIFile, "initWithPath");
+const ZipReader = new Components.Constructor("@mozilla.org/libjar/zip-reader;1", "nsIZipReader", "open");
+
+
+Cu.import("resource://gre/modules/Services.jsm");
+Cu.import("resource://gre/modules/osfile.jsm");
+Cu.import("resource://gre/modules/Task.jsm");
+
+
+/**
+ * Returns a promise that is resolved with a list of files that have one of the
+ * extensions passed, represented by their nsIURI objects, which exist inside
+ * the directory passed.
+ *
+ * @param dir the directory which to scan for files (nsIFile)
+ * @param extensions the extensions of files we're interested in (Array).
+ */
+function generateURIsFromDirTree(dir, extensions) {
+  if (!Array.isArray(extensions)) {
+    extensions = [extensions];
+  }
+  let dirQueue = [dir.path];
+  return Task.spawn(function*() {
+    let rv = [];
+    while (dirQueue.length) {
+      let nextDir = dirQueue.shift();
+      let {subdirs, files} = yield iterateOverPath(nextDir, extensions);
+      dirQueue.push(...subdirs);
+      rv.push(...files);
+    }
+    return rv;
+  });
+}
+
+/**
+ * Uses OS.File.DirectoryIterator to asynchronously iterate over a directory.
+ * It returns a promise that is resolved with an object with two properties:
+ *  - files: an array of nsIURIs corresponding to files that match the extensions passed
+ *  - subdirs: an array of paths for subdirectories we need to recurse into
+ *             (handled by generateURIsFromDirTree above)
+ *
+ * @param path the path to check (string)
+ * @param extensions the file extensions we're interested in.
+ */
+function iterateOverPath(path, extensions) {
+  let iterator = new OS.File.DirectoryIterator(path);
+  let parentDir = new LocalFile(path);
+  let subdirs = [];
+  let files = [];
+
+  let pathEntryIterator = (entry) => {
+    if (entry.isDir) {
+      subdirs.push(entry.path);
+    } else if (extensions.some((extension) => entry.name.endsWith(extension))) {
+      let file = parentDir.clone();
+      file.append(entry.name);
+      let uriSpec = getURLForFile(file);
+      files.push(Services.io.newURI(uriSpec, null, null));
+    } else if (entry.name.endsWith(".ja") || entry.name.endsWith(".jar")) {
+      let file = parentDir.clone();
+      file.append(entry.name);
+      for (let extension of extensions) {
+        let jarEntryIterator = generateEntriesFromJarFile(file, extension);
+        files.push(...jarEntryIterator);
+      }
+    }
+  };
+
+  return new Promise((resolve, reject) => {
+    Task.spawn(function* () {
+      try {
+        // Iterate through the directory
+        yield iterator.forEach(pathEntryIterator);
+        resolve({files: files, subdirs: subdirs});
+      } catch (ex) {
+        reject(ex);
+      } finally {
+        iterator.close();
+      }
+    });
+  });
+}
+
+/* Helper function to generate a URI spec (NB: not an nsIURI yet!)
+ * given an nsIFile object */
+function getURLForFile(file) {
+  let fileHandler = Services.io.getProtocolHandler("file");
+  fileHandler = fileHandler.QueryInterface(Ci.nsIFileProtocolHandler);
+  return fileHandler.getURLSpecFromActualFile(file);
+}
+
+/**
+ * A generator that generates nsIURIs for particular files found in jar files
+ * like omni.ja.
+ *
+ * @param jarFile an nsIFile object for the jar file that needs checking.
+ * @param extension the extension we're interested in.
+ */
+function* generateEntriesFromJarFile(jarFile, extension) {
+  let zr = new ZipReader(jarFile);
+  let entryEnumerator = zr.findEntries("*" + extension + "$");
+
+  const kURIStart = getURLForFile(jarFile);
+  while (entryEnumerator.hasMore()) {
+    let entry = entryEnumerator.getNext();
+    // Ignore the JS cache which is stored in omni.ja
+    if (entry.startsWith("jsloader") || entry.startsWith("jssubloader")) {
+      continue;
+    }
+    let entryURISpec = "jar:" + kURIStart + "!/" + entry;
+    yield Services.io.newURI(entryURISpec, null, null);
+  }
+  zr.close();
+}
+
+