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🌎 e7n: Chrome Extension Internationalization

l10n ➡️ localization “refers to the adaptation of a product, application or document content to meet the language, cultural and other requirements of a specific target market (a locale).” -W3C

i18n ➡️ internationalization “is the design and development of a product, application or document content that enables easy localization for target audiences that vary in culture, region, or language.” -W3C

e7n ➡️ extension “is a library for making it easier to use the chrome.i18n infrastructure” -@mrcoles

This tool auto-populates _locales/<default_locale>/messages.json with strings found in a Chrome extension project, and makes it easy to convert from those strings into localized text.

1. Mark up localizable strings

HTML

Mark HTML tags with a data-e7n tag. Such tags should only contain text (or comments):

<div>
  <span data-e7n>Hello!</span>
  <img src="foo.png" />
</div>

The i18n key is auto-derived from the text. You can also manually specify the key by setting a value on the data attr, e.g., data-e7n="hello".

The content will automatically get HTML-escaped, if you want to parse raw HTML, e.g., if you have a link in the text, then add the data-e7n-html to the markup too:

<p data-e7n data-e7n-html>More info <a href="https://example.com/">here</a>.</p>

JavaScript

Use the e7n tr JavaScript function to signify text that is a localizable string. Use string literals or variables that are string literals.

This can run in JavaScript, Typescript, and JSX code—it will look for files matching the glob **/*.{js,jsx,ts,tsx}.

import { tr } from 'e7n';

// auto-generated key
const FOO = tr('This is a localized string.');

// manually specified key
const BAR = tr('This is also localized', 'bar');

// auto-generated key from concatenated string literals
const MULTI = tr('This is combined ' + 'via plus signs');

// with placeholders (you can also set the key 2nd arg to `null`)
const BAZ = tr(
  'Hi, $name$, your number is $number$.',
  'hiYourNumber',
  ['Alice', '10'],
  {
    name: { content: '$1', example: 'Alyssa P' },
    number: { content: '$2', example: '1' }
  }
);

2. Setup auto-conversion

In HTML files, auto-convert your marked tags with the updateHtml function:

import { updateHtml } from 'e7n';

document.addEventListener('DOMContentLoaded', event => {
  updateHtml();
});

const update = () => {
  fetch('/something')
    .then(r => r.text())
    .then(html => {
      let elt = document.getElementById('something');
      elt.innerHTML = html;
      updateHtml(elt);
    });
};

In JavaScript files, the tr function will already convert messages for you.

Pseudo-localization

You can enable pseudo-localization (sometimes called "pseudoloc") by setting the pseudoloc option to true.

import { options as e7nOptions } from 'e7n';

e7nOptions.pseudoloc = true;

This can let you test to make sure parts of your UI are connected up properly without having to change your browser's language.

For example "Delete image" would get convrted to: "Ḓḗḗŀḗḗŧḗḗ īḿȧȧɠḗḗ".

3. Build project

Generate your _locales/<default_locale>/messages.json file via the following steps:

Add a "default_locale" value to your extension’s manifest.json file, e.g., "default_locale": "en",
Create a starting messages.json file: mkdir -p _locales/en/ && echo '{}' > _locales/en/messages.json (TODO: automate this more, so you don't need to create the directory or file)
Run e7n: e7n [path_to_src_directory_with_manifest]

The build will fail if it encounters issues generating the messages. If it succeeds, it will print out the JSON for the new file and also update the file in place.