0 comments on “Sitecore Page Speed: Part 3: Eliminate JS Loading Time”

Sitecore Page Speed: Part 3: Eliminate JS Loading Time

In part 1 & part 2 of our Sitecore page speed blog, we covered off:

  • The Google Page Speed Insights tool.
  • We looked at a node tool called critical that could generate above the fold (critical viewport) CSS code that is minified.
  • We referenced the way in which Google recommends deferring CSS loading.
  • We showed a way to integrate “Above The Fold” CSS into a Helix based project and achieve a page free of render blocking CSS.

In this 3rd part of the series, we will introduce a way to defer the load of all external javascript assets (async).

A reminder that I have committed the sample code for this blog into a fork of the helix habitat example project. You can find the sample here. For a direct comparison of changes made to achieve these page load enhancements, view a side by side comparison here.

Dynamic JS loading Installation Steps:

  1. Inside Sitecore add a new view Rendering that reference the file /Views/Common/Assets/Scripts-3.2.1.cshtml
    • Note down the ID of this rendering and replace in the ID of the rendering in the next step.
  2. Update the Default.cshtml layout to include a new cached rendering.
  3.  @*Scripts Legacy Jquery jquery-3.2.1 *@
     @Html.Sitecore().CachedRendering("{B0DD36CE-EE4A-4D01-9986-7BEF114196DD}", new RenderingCachingSettings { Cacheable = true, CacheKey = cacheKey + "_bottom_scripts" })
    • cacheKey = This variable is something unique that will identify the page. You could use the Sitecore context Item ID or path for example.


The rendering Scripts-3.2.1.cshtml will render out the following javascript onto the page:

var scriptsToLoad = ['//cdnjs.cloudflare.com/ajax/libs/modernizr/2.8.3/modernizr.min.js','//maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js','/assets/js/slick.min.js','/assets/js/global.js','/assets/js/Script.js','/assets-legacy/js/lib/lazyload.min.js'];
src="/assets-legacy/js/lib/jquery-3.2.1.min.js" async defer>
  • First of all, it prints out a JS array of all the scripts that this page requires.
    • This is the array of JS files that comes from Themes and Page Assets inside the CMS. If you are familiar with Habitat Helix this list can be content managed inside the CMS.
  • It then instructs the jquery library to be loaded async (which will not block the network download of the page response).
  • Once jquery is loaded, this modified version of jquery contains some code at the end that will read in the list of scripts dynamically and apply them to the page.
    • This is achieved with fairly simple AJAX load calls to the script URLs.


Once integrated successfully you will end up with a page that does not contain any blocking JS network calls.  The Google Page Speed tool should give you a nice score boost for your achievement in reducing initial load time.

Hints and Tips:

Bootstrapping JQuery Code:

  • jquery Document.Ready() function calls may not fire inside dynamically loaded JS files. This is because the JS file is loaded after DOM is ready and it’s too late for the Document.Ready() event at this stage.
  • As a workaround, you could code your JS files to bootstrap on both the Document.Ready() or whenever $ is not undefined.
  • In the case of dynamic loading in this manner, because jquery was loaded first, $ should not be undefined and your code should be bootstrapped successfully.

Debugging in chrome:

  • When dynamically loading JS files they may strangely not appear in the chrome console debugger as you would normally expect.
  • The workaround for this is to add a comment to the top of each JS library
  • //# sourceURL=global.js
  • This will cause the chrome debugger to list the file in the source tab under the “(no domain)” heading.
  • You will then be able to debug the file as per normal.
0 comments on “Sitecore Page Speed: Part 2: Inlining CSS into Helix”

Sitecore Page Speed: Part 2: Inlining CSS into Helix

In part 1 of this Sitecore page speed blog, we covered off:

  • The Google Page Speed Insights tool.
  • We looked at a node tool called critical that could generate above the fold (critical viewport) CSS code that is minified.
  • We referenced the way in which Google recommends deferring CSS loading.

In this second part of the Sitecore Page Speed series, I am going to cover off how I would go about achieving this in my Sitecore layout.

Before we dive in I have committed the sample code for this blog into a fork of the helix habitat example project. You can find the sample here. For a direct comparison of changes made to achieve these page load enhancements, view a side by side comparison here.

Installation Steps:


  1. For each page that you want to render above the fold CSS we take the minimised code (we generated in the first blog) and put it on the page within the CMS.
  2. Inside the CMS we also create some new renderings in the common project.
    • These renderings are used in the default.cshtml layout.
    • They point to the CSS rendering code.
    • This wrapping technique provides the ability to cache the rendering so that the code in RenderAssetsService.cs does not need to be executed on every single page load.
    • Take note of the IDs of each rendering you will need to copy them over to the CachedRendering IDs shown in step 3 below.
  3. Update the default.cshtml layout with two key renderings.
    • One in the <head> tag that points to /Views/Common/Assets/InlineStyles.cshtml
    •  @*Inline Styles Rendering*@
       @Html.Sitecore().CachedRendering("{B14DA82E-F844-4945-8F31-4577A52861E1}", new RenderingCachingSettings { Cacheable = true, CacheKey = cacheKey + "_critical_styles" })
    • One just before the </body> closing tag that points to /Views/Common/Assets/StylesDeferred.cshtml
    •  @*Styles Rendering Deferred Styles *@
       @Html.Sitecore().CachedRendering("{F04C562A-CBF9-40CF-8CA9-8CE83FDF0BFA}", new RenderingCachingSettings { Cacheable = true, CacheKey = cacheKey + "_bottom_styles" })

StylesDeferred.cshtml  contains logic that will check for inline CSS on every page. If the page contains Inline CSS then the main CSS files will have their network download deferred until later. On the other hand, if the page does not contain any inline CSS then the main CSS files will be loaded as blocking assets. Doing so ensures that the page displays normally in both situations.

  • The cacheKey variable passed to our CachedRendering is simply something to identify the page as unique.  You could use the Sitecore context item ID or path for example.

If done correctly you should end up with pages that look normal even with the main CSS files deleted (only do this as a test). The CSS will no longer load via another network that blocks the page and your Google Page Speed rank should recieve a boost.

0 comments on “Sitecore Helix: Lets Talk Layers”

Sitecore Helix: Lets Talk Layers

Here are some notes from the decision-making process our team uses with regard to what goes where and in which layer. Of course, the helix documentation does go over the guidelines but it’s not until you start working with the architecture that things begin to become clear.

Project Layer

Definition: The Project layer provides the context of the solution. This means the actual cohesive website or channel output from the implementation, such as the page types, layout and graphical design. It is on this layer that all the features of the solution are stitched together into a cohesive solution that fits the requirements.

Comment: The project layer is probably the most straightforward layer to understand. In our project, the modules in this layer remained lightweight and mostly contain razor view files that allow content editors to build up the HTML structure of the pages.

The website content (under home), page templates and component templates are serialized by Unicorn and also live in this layer.

It’s also worth mentioning one particular gotcha you may hit in development to do with template inheritance and you can read more in this blog post.

Feature or Foundation?

Feature Definition: The Feature layer contains concrete features of the solution as understood by the business owners and editors of the solution, for example news, articles, promotions, website search, etc. The features are expressed as seen in the business domain of the solution and not by technology, which means that the responsibility of a Feature layer module is defined by the intent of the module as seen by a business user and not by the underlying technology. Therefore, the module’s responsibility and naming should never be decided by specific technologies but rather by the module’s business value or business responsibility.

Discussion: For our feature modules, we aimed for single concrete features that are independent of each other. They may contain views, templates, controllers, renderings, configuration changes and related business logic code to tie it all together. The point is to always stick to the rule: “Classes that change together are packaged together”.

When building feature modules, it’s also very handy to think about the feature modules removal as you build it. Keep asking yourself how easy would it be to roll back this module and what would I need to do. Doing so will help you to keep those dependencies under control.

Foundation Definition: The lowest level layer in Helix is the Foundation layer, which as the name suggests forms the foundation of your solution. When a change occurs in one of these modules it can impact many other modules in the solution. This mean that these modules should be the most stable in your solution in term of the Stable Dependencies Principle.


Discussion: We found that our foundation modules usually consist of frameworks or code that provide a structural functionality to support the web application as a whole. Each foundation module may be used by multiple feature modules to provide them with the support they need to run properly. Our foundation modules contain API calls, configuration, ORM structures (Glass Mapper), initialisation code, interfaces and abstract base classes.

An important point is that unlike feature layer modules, the foundation layer modules can have dependencies to other foundation layer modules. If this was not the case it would be very difficult to construct the foundation layer in the first place.

For the most part, the team can make some fairly quick decisions about what goes where in the initial project planning. And what goes where is fairly obvious after you get familiar with the habitat example project. The main dilemma you’re going to encounter is around where your repositories and services (key business logic) might need to sit.

Business LogicWhat goes where! Help!

Let’s consider the definitions above, they seem straightforward enough. However, in agile projects where things may change rapidly or requirements are not immediately clear (which happens a lot), you’re inevitably going to need to make some judgment calls.

What am I talking about with the above statement, well let’s say one developer codes up a feature module at the beginning of that project. At first, it seems like that particular portion of code is only required by that particular feature. Down the track a requirement surfaces whereby the same business logic needs to be used in another Feature module. Helix rules dictate:

  • Classes that change together are packaged together.
  • No dependencies between feature projects should exist.

A lesser developer may be tempted at this point to duplicate the code in both feature modules to get the job done quickly. This, however, breaks some fairly important fundamental coding standards that many of us try to stick to. Step back to consider the technical debt that duplicate code leave behind vs dependencies between your Helix feature modules.

The solution to this dilemma; it’s time to refactor that feature logic and move it into the foundation layer. After which any feature modules that needs to reference the same code can reference it in the foundation layer.

Remember “with great power comes great responsibility” and this is especially true when touching code in the foundation layer. The code you touch in the foundation layer should be highly stable and well tested as the helix guidelines suggest.

Was the original decision a mistake?

On the flip side of the coin its worth considering that it wasn’t a mistake to put that piece of code in the feature layer to start with. Technically if no one else needed to use the code at the time and it was reasonably unforeseen that anyone else would need to use it, then it probably was the correct call.

Accept that things may change

The team members on your helix project will need to be flexible and accepting of change. I think it’s worth being prepared for some open discussions within your team about what goes in the foundation layer and what goes in the feature layer. It’s certainly going to be open to interpretation and a topic of debate. A team that can work together and be open to a change of direction within their code structure will help the code base stay within the helix guidelines as the project evolves.

Good luck!