Wayfair Tech Blog

Tungsten.js: UI Framework with Virtual DOM + Mustache Templates


Performance is top priority here at Wayfair, because improved performance means an improved customer experience. A significant piece of web performance is the time it takes to render, or generate, the markup for a page. Over the last several months we've worked hard to improve the render performance on our customer facing sites, and ensure it's easier for our engineers to write code that results in page renders with optimal performance.

We had been using Backbone.js and Mustache templates for our JavaScript modules at Wayfair for some time, but last year we realized that our front-end performance needed an upgrade. We identified two areas for improvement: efficiency of client-side DOM updates and abstracting DOM manipulation away from engineers.

The first issue was a result of the standard render implementation in Backbone. By default, the Backbone render implementation does nothing. It is up to developers to implement the render function as they see fit. A common implementation of this (and the example given in Backbone Docs) looks something like this:

render: function() {

The problem with this implementation is two-fold: first, the entire view is unnecessarily re-rendered with jQuery's $().html() whenever render is called, and second, the render method always manipulates the DOM regardless of whether the data changed, so engineers must be explicit about when render is called to avoid unnecessary expensive DOM updates. The solution to both of these problems is a mix of only calling render when the engineer is sure the entire view needs to be re-rendered and then writing low-level DOM manipulation code when only portions of the view need to be updated, or the update needs to be more precise (e.g., changing a single class on an element in the view). All of this means that engineers have to be very aware of the state of the DOM at all times, and have to be aware of the performance consequences of any DOM manipulations. This makes for view modules that are hard to reason about and include low-level DOM manipulation code.

To address both of these problems, we investigated front-end frameworks that would abstract the DOM from the developer while also providing high-performance updates. The primary library we looked at was React.js, a UI library open-sourced by Facebook that utilizes a one-way data flow with virtual DOM rendering to support high-performance client-side DOM updates. We really liked React.js, but encountered one major issue: the lack of support for templates which enabled high-performance server-side rendering.

On modern web sites and applications, HTML rendering occurs at two points: once on page load when the DOM is built from HTML delivered from the server, and again (0 to many times) when JavaScript updates the DOM after page load, usually as a result of the user interacting with the page. The initial rendering happens on the server with a multi-page site like Wayfair, and we've put a lot of work into making sure it's as fast as it can be. HTML markup is written in Mustache templates and rendered via a C++ mustache renderer implemented as an extension for PHP. This gives us server-side rendering at speeds faster even than native PHP views.

Since server-side rendering is an important part of our web site, we were glad that React.js comes with this feature out of the box. Unfortunately while server-side rendering is available with React.js, it's significantly slower than our existing C++ Mustache setup. In addition to performance, rendering React.js on the server would have required Node.js servers to supplement our PHP servers. This new requirement for UI rendering would have introduced complexity as well as a new single point of failure into our server stack. For these reasons, as well as the fact that we already had existing Mustache templates we wished to reuse, we decided React.js wasn't a good fit.

Where do we go from here? We liked many of the concepts React.js introduced us to, such as reactive data-driven views and virtual DOM rendering, but we didn't want our choice of a front-end framework to dictate our server-side technologies, and dictate a replacement of Mustache rendering via C++ and PHP. So, after some investigation of what else was available, we decided to take the concepts we liked from React.js and implement them ourselves with features that made sense for our tech stack.

Earlier this year, we wrote Tungsten.js, a modular web UI framework that leverages shared Mustache templates to enable high-performance rendering on both server and client. A few weeks ago we announced that we were open sourcing Tungsten.js, and today we're excited to announce that primary development on Tungsten.js will be "GitHub first," and all new updates to the framework can be found on our GitHub repo: https://github.com/wayfair/tungstenjs.

Tungsten.js is the bridge we built between Mustache templates, virtual-DOM, and Backbone.js. It uses the Ractive compiler to pre-compile Mustache templates to functions that return virtual DOM objects. It uses the virtual-DOM diff/patch library to make intelligent updates to the DOM. And it uses Backbone.js views, models, and collections as the developer-facing API. At least, it uses all these libraries for us here at Wayfair. Tungsten.js emphasizes modularity above all else. Any one of these layers in Tungsten.js can be swapped out for a similar library paired with an adaptor. Backbone could be swapped out for Ampersand. virtual-DOM could be swapped out another implementation. Mustache could be swapped out for Handlebars, Jade, or even JSX. So, more generally, Tungsten.js is a bridge between any combination of markup notation (templates), a UI updating mechanism, and a view layer for developers.

We don't expect Tungsten.js to be the best fit for everyone, but we think it fits a common set of uses cases very well. We've been using it on customer-facing pages in production for a while here at Wayfair and so far we've been very happy with it. Our full-stack engineers frequently tell us they far prefer using Tungsten to vanilla Backbone.js + jQuery, and we've improved client-side performance now that DOM manipulation is abstracted away from developers. And while we weren't trying to be the "fastest" front-end framework around, it turns out that when we re-implemented Ryan Florance's DBMonster demo from React.js Conf in Tungsten.js, the browser's frame rate ends up being, give or take, at the same level as both React and Ember with Glimmer.

Here at Wayfair we have a saying that "we're never done". That's certainly the case with Tungsten.js, which we're constantly improving. We have a lot of ideas for Tungsten.js in the coming months, so watch the repo for updates. And of course we welcome contributions!