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Localizing a webapp with webL10n.js

3 min read

I am currently working on a Velib webapp. With √Člie, we modularized everything so that the backend API can be edited easily, and adapted to any other bike sharing system, hence we wanted it to be easily localizable and looked for solutions compatible with as many browsers as possible. We finally chose webL10n.js. Here are some explanations about it and how to use it.

Why webL10n.js?

First thing is: why choose webL10n.js instead of anything else? We found basically four solutions: webL10n.js, L20n.js, Jed and a modified version of webL10n.js used in Gaia.

Jed takes a really different approach and, especially as we are not really familiar with localizing content, we found it more difficult to use and integrate.

The three others take a really simple approach. They use extra data-* attributes on any tag to replace on the fly the textContent of the node by a translation found in a formatted file. It is really easy to integrate, use and tweak. They support advanced features such as pluralization, HTML modifications, responsive localization (to use a different localization file on small screens), etc.

WebL10n.js and the modified version in Gaia are basically the same, except that the one in Gaia dropped hacks to add support in some old browsers such as IE6. Plus webL10n is in a separate git repo which is easy to track, so I'd rather go with this one. But the documentation is not really complete and the associated MDN wiki page is outdated. Hence this blog post :) Don't worry about the lack of recent commits on webL10n.js, it is stable and usable (and still maintained and supported by kaze).

L20n.js is the latest Mozilla project aiming at replacing webL10n.js. I had many problems with it, because the API keeps moving, and no doc is in sync with the code. Downloadable version exposes a totally different API than the one in the git repo, and the doc is not really helpful concerning which version should be considered stable. Plus the l20n file format is really weird and I'd rather not reinvent the wheel and go with standard properties file to ease translation for contributors.

Demo and extra infos

For more informations, you can refer to the README.

For an app using it, you can have a look at our VelibFxos webapp, espcially this folder. You can also see it in your browser at https://velib.phyks.me/ (under heavy work in progress, so might break from time to time).

Note: Note that there is a bug when mixing pluralization and innerHTML, which can be worked around. See this Github issue.

EDIT: Since I initially wrote this article, I came across Polyglot.js, a JS library by Airbnb, which does exactly this. It looks really nice and trustable, especially since it is backed by Airbnb which is heavily using it. One major drawback is that is uses a non-standard format for translations, instead of a po file or a properties file. But it could be easy to plug such a parser into it. It supports basically the same features as webl10n.js, except that it only has a JS API, without support for extra data- parameters. This is ok if you render your templates in JS (using React or Angular for instance), but I find it more difficult than webl10n.js to use in other cases.

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