diff --git a/browser/base/content/browser-feeds.js b/browser/base/content/browser-feeds.js
index 7bba3954082..5c5d4b2a892 100644
--- a/browser/base/content/browser-feeds.js
+++ b/browser/base/content/browser-feeds.js
@@ -95,7 +95,7 @@ var FeedHandler = {
     var feedURI = makeURI(href, document.characterSet);
     // Use the feed scheme so X-Moz-Is-Feed will be set
     // The value doesn't matter
-    if (/^https?$/.test(feedURI.scheme))
+    if (/^https?/.test(feedURI.scheme))
       href = "feed:" + href;
     this.loadFeed(href, event);
   },
diff --git a/browser/base/content/browser-safebrowsing.js b/browser/base/content/browser-safebrowsing.js
index a34233d0db6..96cf1f35897 100644
--- a/browser/base/content/browser-safebrowsing.js
+++ b/browser/base/content/browser-safebrowsing.js
@@ -8,7 +8,7 @@ var gSafeBrowsing = {
   setReportPhishingMenu: function() {
 
     // A phishing page will have a specific about:blocked content documentURI
-    var isPhishingPage = content.document.documentURI.startsWith("about:blocked?e=phishingBlocked");
+    var isPhishingPage = /^about:blocked\?e=phishingBlocked/.test(content.document.documentURI);
 
     // Show/hide the appropriate menu item.
     document.getElementById("menu_HelpPopup_reportPhishingtoolmenu")
diff --git a/browser/base/content/browser-tabPreviews.js b/browser/base/content/browser-tabPreviews.js
index c90480b143b..2e0c082c598 100644
--- a/browser/base/content/browser-tabPreviews.js
+++ b/browser/base/content/browser-tabPreviews.js
@@ -735,7 +735,7 @@ var allTabs = {
   },
 
   handleEvent: function allTabs_handleEvent(event) {
-    if (event.type.startsWith("Tab")) {
+    if (/^Tab/.test(event.type)) {
       var tab = event.target;
       if (event.type != "TabOpen")
         var preview = this._getPreview(tab);
diff --git a/browser/base/content/browser.js b/browser/base/content/browser.js
index e3f72f435a8..917719d46fb 100644
--- a/browser/base/content/browser.js
+++ b/browser/base/content/browser.js
@@ -2521,13 +2521,13 @@ let BrowserOnClick = {
 
     // If the event came from an ssl error page, it is probably either the "Add
     // Exception…" or "Get me out of here!" button
-    if (ownerDoc.documentURI.startsWith("about:certerror")) {
+    if (/^about:certerror/.test(ownerDoc.documentURI)) {
       this.onAboutCertError(originalTarget, ownerDoc);
     }
-    else if (ownerDoc.documentURI.startsWith("about:blocked")) {
+    else if (/^about:blocked/.test(ownerDoc.documentURI)) {
       this.onAboutBlocked(originalTarget, ownerDoc);
     }
-    else if (ownerDoc.documentURI.startsWith("about:neterror")) {
+    else if (/^about:neterror/.test(ownerDoc.documentURI)) {
       this.onAboutNetError(originalTarget, ownerDoc);
     }
     else if (/^about:home$/i.test(ownerDoc.documentURI)) {
@@ -4481,7 +4481,7 @@ var TabsProgressListener = {
 
     if (aStateFlags & Ci.nsIWebProgressListener.STATE_STOP &&
         Components.isSuccessCode(aStatus) &&
-        aWebProgress.DOMWindow.document.documentURI.startsWith("about:")) {
+        /^about:/.test(aWebProgress.DOMWindow.document.documentURI)) {
       aBrowser.addEventListener("click", BrowserOnClick, true);
       aBrowser.addEventListener("pagehide", function onPageHide(event) {
         if (event.target.defaultView.frameElement)
diff --git a/browser/base/content/pageinfo/pageInfo.js b/browser/base/content/pageinfo/pageInfo.js
index 27a42d8594c..cbabcab36ae 100644
--- a/browser/base/content/pageinfo/pageInfo.js
+++ b/browser/base/content/pageinfo/pageInfo.js
@@ -161,7 +161,7 @@ gImageView.getCellProperties = function(row, col, props) {
   var item = gImageView.data[row][COL_IMAGE_NODE];
   if (!checkProtocol(data) ||
       item instanceof HTMLEmbedElement ||
-      (item instanceof HTMLObjectElement && !item.type.startsWith("image/"))
+      (item instanceof HTMLObjectElement && !/^image\//.test(item.type)))
     props.AppendElement(this._brokenAtom);
 
   if (col.element.id == "image-address")
@@ -945,7 +945,7 @@ function makePreview(row)
       mimeType = getContentTypeFromHeaders(cacheEntry);
 
     // if we have a data url, get the MIME type from the url
-    if (!mimeType && url.startsWith("data:")) {
+    if (!mimeType && /^data:/.test(url)) {
       let dataMimeType = /^data:(image\/[^;,]+)/i.exec(url);
       if (dataMimeType)
         mimeType = dataMimeType[1].toLowerCase();
@@ -987,7 +987,7 @@ function makePreview(row)
     if ((item instanceof HTMLLinkElement || item instanceof HTMLInputElement ||
          item instanceof HTMLImageElement ||
          item instanceof SVGImageElement ||
-         (item instanceof HTMLObjectElement && mimeType.startsWith("image/")) || isBG) && isProtocolAllowed) {
+        (item instanceof HTMLObjectElement && /^image\//.test(mimeType)) || isBG) && isProtocolAllowed) {
       newImage.setAttribute("src", url);
       physWidth = newImage.width || 0;
       physHeight = newImage.height || 0;
diff --git a/browser/base/content/pageinfo/permissions.js b/browser/base/content/pageinfo/permissions.js
index 511139bd1f7..210327802ed 100644
--- a/browser/base/content/pageinfo/permissions.js
+++ b/browser/base/content/pageinfo/permissions.js
@@ -83,7 +83,7 @@ function onLoadPermission()
 
   var uri = gDocument.documentURIObject;
   var permTab = document.getElementById("permTab");
-  if (/^https?$/.test(uri.scheme)) {
+  if(/^https?/.test(uri.scheme)) {
     gPermURI = uri;
     var hostText = document.getElementById("hostText");
     hostText.value = gPermURI.host;
diff --git a/browser/base/content/urlbarBindings.xml b/browser/base/content/urlbarBindings.xml
index f69a29d0fe2..344da99d995 100644
--- a/browser/base/content/urlbarBindings.xml
+++ b/browser/base/content/urlbarBindings.xml
@@ -645,7 +645,7 @@
       <method name="_parseActionUrl">
         <parameter name="aUrl"/>
         <body><![CDATA[
-          if (!aUrl.startsWith("moz-action:"))
+          if (!/^moz-action:/.test(aUrl))
             return null;
 
           // url is in the format moz-action:ACTION,PARAM
@@ -1615,7 +1615,7 @@
           // otherwise just rely on the panel id for common arrowpanels.
           let type = this._panel.firstChild.getAttribute("popupid") ||
                      this._panel.id;
-          if (type.startsWith("password-"))
+          if (/^password-/.test(type))
             return "passwords";
           if (type == "editBookmarkPanel")
             return "bookmarks";
diff --git a/browser/components/certerror/test/browser_bug431826.js b/browser/components/certerror/test/browser_bug431826.js
index 5d07b590519..0a9c70e10b2 100644
--- a/browser/components/certerror/test/browser_bug431826.js
+++ b/browser/components/certerror/test/browser_bug431826.js
@@ -12,7 +12,7 @@ function testBrokenCert() {
   window.removeEventListener("DOMContentLoaded", testBrokenCert, true);
 
   // Confirm that we are displaying the contributed error page, not the default
-  ok(gBrowser.contentDocument.documentURI.startsWith("about:certerror"), "Broken page should go to about:certerror, not about:neterror");
+  ok(/^about:certerror/.test(gBrowser.contentDocument.documentURI), "Broken page should go to about:certerror, not about:neterror");
 
   // Confirm that the expert section is collapsed
   var expertDiv = gBrowser.contentDocument.getElementById("expertContent");
diff --git a/browser/components/downloads/src/DownloadsCommon.jsm b/browser/components/downloads/src/DownloadsCommon.jsm
index 230471688cd..a36788e59ea 100644
--- a/browser/components/downloads/src/DownloadsCommon.jsm
+++ b/browser/components/downloads/src/DownloadsCommon.jsm
@@ -864,7 +864,7 @@ DownloadsDataItem.prototype = {
     // The download database may contain targets stored as file URLs or native
     // paths.  This can still be true for previously stored items, even if new
     // items are stored using their file URL.  See also bug 239948 comment 12.
-    if (this.file.startsWith("file:")) {
+    if (/^file:/.test(this.file)) {
       // Assume the file URL we obtained from the downloads database or from the
       // "spec" property of the target has the UTF-8 charset.
       let fileUrl = NetUtil.newURI(this.file).QueryInterface(Ci.nsIFileURL);
diff --git a/browser/components/feeds/src/FeedWriter.js b/browser/components/feeds/src/FeedWriter.js
index ea26b2b9cbb..b79fa5abdef 100644
--- a/browser/components/feeds/src/FeedWriter.js
+++ b/browser/components/feeds/src/FeedWriter.js
@@ -1340,7 +1340,7 @@ FeedWriter.prototype = {
   _setFaviconForWebReader:
   function FW__setFaviconForWebReader(aReaderUrl, aMenuItem) {
     var readerURI = makeURI(aReaderUrl);
-    if (!/^https?$/.test(readerURI.scheme)) {
+    if (!/^https?/.test(readerURI.scheme)) {
       // Don't try to get a favicon for non http(s) URIs.
       return;
     }
diff --git a/browser/components/places/content/controller.js b/browser/components/places/content/controller.js
index 5c4d27689cf..e0ee8bef10f 100644
--- a/browser/components/places/content/controller.js
+++ b/browser/components/places/content/controller.js
@@ -1425,13 +1425,13 @@ let PlacesControllerDragHelper = {
       if (ip.isTag && ip.orientation == Ci.nsITreeView.DROP_ON &&
           dragged.type != PlacesUtils.TYPE_X_MOZ_URL &&
           (dragged.type != PlacesUtils.TYPE_X_MOZ_PLACE ||
-           dragged.uri.startsWith("place:")))
+           /^place:/.test(dragged.uri)))
         return false;
 
       // The following loop disallows the dropping of a folder on itself or
       // on any of its descendants.
       if (dragged.type == PlacesUtils.TYPE_X_MOZ_PLACE_CONTAINER ||
-          dragged.uri.startsWith("place:")) {
+          /^place:/.test(dragged.uri)) {
         let parentId = ip.itemId;
         while (parentId != PlacesUtils.placesRootId) {
           if (dragged.concreteId == parentId || dragged.id == parentId)
diff --git a/browser/components/preferences/applications.js b/browser/components/preferences/applications.js
index ef192e6d971..f94cfc900ac 100644
--- a/browser/components/preferences/applications.js
+++ b/browser/components/preferences/applications.js
@@ -1887,7 +1887,7 @@ var gApplicationsPane = {
     // that template (i.e. with %s in the template replaced by the URL of the
     // content being handled).
 
-    if (/^https?$/.test(uri.scheme) && this._prefSvc.getBoolPref("browser.chrome.favicons"))
+    if (/^https?/.test(uri.scheme) && this._prefSvc.getBoolPref("browser.chrome.favicons"))
       return uri.prePath + "/favicon.ico";
 
     return "";
diff --git a/browser/components/preferences/in-content/applications.js b/browser/components/preferences/in-content/applications.js
index 69fad1af84d..30bf7b0bb32 100755
--- a/browser/components/preferences/in-content/applications.js
+++ b/browser/components/preferences/in-content/applications.js
@@ -1874,7 +1874,7 @@ var gApplicationsPane = {
     // they'll only visit URLs derived from that template (i.e. with %s
     // in the template replaced by the URL of the content being handled).
 
-    if (/^https?$/.test(uri.scheme) && this._prefSvc.getBoolPref("browser.chrome.favicons"))
+    if (/^https?/.test(uri.scheme) && this._prefSvc.getBoolPref("browser.chrome.favicons"))
       return uri.prePath + "/favicon.ico";
 
     return "";
diff --git a/browser/components/safebrowsing/content/blockedSite.xhtml b/browser/components/safebrowsing/content/blockedSite.xhtml
index b56875eb6ca..dab41b8141e 100644
--- a/browser/components/safebrowsing/content/blockedSite.xhtml
+++ b/browser/components/safebrowsing/content/blockedSite.xhtml
@@ -51,7 +51,7 @@
         url = decodeURIComponent(match[1]);
 
         // If this is a view-source page, then get then real URI of the page
-        if (url.startsWith("view-source:"))
+        if (/^view-source\:/.test(url))
           url = url.slice(12);
         return url;
       }
diff --git a/browser/components/tabview/test/browser_tabview_bug600645.js b/browser/components/tabview/test/browser_tabview_bug600645.js
index c79f72b364d..7f49b09c976 100644
--- a/browser/components/tabview/test/browser_tabview_bug600645.js
+++ b/browser/components/tabview/test/browser_tabview_bug600645.js
@@ -50,7 +50,7 @@ function onTabPinned() {
 
       // with moz-anno:favicon automatically redirects to the default favIcon 
       // if the given url is invalid
-      ok(iconSrc.startsWith("moz-anno:favicon:"),
+      ok(/^moz-anno:favicon:/.test(iconSrc),
          "The icon url starts with moz-anno:favicon so the default fav icon would be displayed");
 
       // At this point, as an additional integrity check we could also verify