Facebook makes Hermes JavaScript engine available on GitHub

Facebook has made JavaScript engine Hermes available on GitHub so that any developer can use it. The engine needs to optimize large applications on Android devices, reports VentureBeat.

The introduction of the new JavaScript engine is the latest in a series of open-source activities from Facebook. Mobile apps are getting bigger and bigger, which can cause problems for devices with limited storage space or computing power, for example. This is one of the reasons why many large companies, including Spotify, Uber and Facebook themselves, have launched the lite versions of their apps. Developing your own engine would address this problem from the other side by making the apps run better and reducing the download size because the engine is optimized.

Facebook had already planned to do this with its apps, the engine of which is now available. “To improve the performance of Facebook’s apps, we have teams that continuously improve our JavaScript code and platforms,” the company writes in a blog post. “When we analyzed the performance data of our apps, we noticed that the JavaScript engine itself was an important factor in boot performance and download size. With this data, we knew that we needed to optimize JavaScript performance in relation to the limitations of a mobile phone, rather than a desktop or laptop”.

React Native

According to Facebook, Hermes helps to improve three important features: time-to-interact (TTI), the time from the start of an app until it is fully loaded and usable, the download size for the Android .APK format and the memory usage. The benefits of the engine could lead to a revival of React Native, a mobile app framework that was already introduced by Facebook in 2015, but has not been very well received so far. One reason for this was that native code was still required for specific functions in apps. As a result, developers always had to connect their native code to React Native.