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Localize: Translate Text

As a function

export const asFunction = () => {
  const wrapper = document.createElement('div');
  let message = 'Loading...';
  function update() {
    message = localize.msg('lit-html-example:body');
    render(
      html`
        <p>${message}</p>
        <sb-locale-switcher></sb-locale-switcher>
      `,
      wrapper,
    );
  }
  localize
    .loadNamespace({
      'lit-html-example': locale => import(`./assets/${locale}.js`),
    })
    .then(() => {
      update();
    });
  localize.addEventListener('localeChanged', () => {
    localize.loadingComplete.then(() => update());
  });
  return wrapper;
};
localize.msg('lit-html-example:body'); // for en-GB: I am from England
localize.msg('lit-html-example:body'); // for nl-NL: Ik kom uit Nederland
// ...

Web Component

For use in a web component we have LocalizeMixin that lets you define namespaces and awaits loading of those translations.

export const webComponent = () => {
  class MessageExample extends LocalizeMixin(LitElement) {
    static get localizeNamespaces() {
      return [
        { 'lit-html-example': locale => import(`./assets/translations/${locale}.js`) },
        ...super.localizeNamespaces,
      ];
    }

    render() {
      return html`
        <div aria-live="polite">
          <p>${localize.msg('lit-html-example:body')}</p>
        </div>
      `;
    }
  }
  if (!customElements.get('message-example')) {
    customElements.define('message-example', MessageExample);
  }
  return html`
    <message-example></message-example>
    <sb-locale-switcher></sb-locale-switcher>
  `;
};
class MessageExample extends LocalizeMixin(LitElement) {
  render() {
    return html`
      <div aria-live="polite">
        <p>${localize.msg('lit-html-example:body')}</p>
      </div>
    `;
  }
}

Google Translate integration

When Google Translate is enabled, it takes control of the html[lang] attribute. Below, we find a simplified example that illustrates this.

The problem

A developer initializes a page like this (and instructs localize to fetch data for en-US locale)

<html lang="en-US"></html>

If Google Translate is enabled and set to French, it will change html[lang]: to <html lang="fr">

Now localize will fetch data for locale fr. There are two problems here:

  • There might be no available data for locale fr
  • Let's imagine data were loaded for fr. If Google Translate is turned off again, the page content will consist of a combination of different locales.

How to solve this

To trigger support for Google Translate, we need to configure two attributes

<html lang="en-US" data-localize-lang="en-US"></html>
  • html[data-localize-lang] will be read by localize and used for fetching data
  • html[lang] will be configured for accessibility purposes (it will makes sure the page is accessible if localize would be lazy loaded).

When Google Translate is set to French, we get: <html lang="fr" data-localize-lang="en-US">

The page is accessible and localize will fetch the right resources