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Bryan Ollendyke
Bryan Ollendyke

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i18n-manager web component

i18n-manager is an element and helpers classes produced to help us manage our i18n needs in web components.

Recapping requirements:

  • Must work without requiring dependencies to adopt
  • Must have good / simple DX
  • Must work with multiple translation files

Goal is to translate ALL of our elements but ultimately supply full internationalization support for the HAX editor, a complex Mobx powered series of web components to transform web editing.

What integration looks like

Here's a simple example of an integration using our @lrnwebcomponents/self-check web component. (code simplified to highlight integration only)

import { LitElement, html, css, svg } from "lit-element/lit-element.js";
import { I18NMixin } from "@lrnwebcomponents/i18n-manager/lib/I18NMixin.js";

class SelfCheck extends I18NMixin(LitElement) {
  constructor() {
    this.t = {
      reveal: "Reveal Answer",
      close: "Close",
      more: "More information",
      context: this,
      basePath: import.meta.url,
      locales: ["en-UK", "ja"],
  static get styles() {
    return [
        :host {
          display: block;
          margin: 15px 0;
  render() {
    return html`
    <div class="card">
      <simple-tooltip aria-hidden="true" for="checkBtn" position="left">
      <user-action track="click" every
        ><a href="${}" target="_blank"
window.customElements.define(SelfCheck.tag, SelfCheck);
export { SelfCheck };
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This has 4 key parts:

  • I18NMixin is applied to LitElement base class.
  • this.t = {} has keys which are then supplying strings.
  • this.registerTranslation supplies the context, a reference to the current file location (the import.meta.url) portion and then an Array of locales that it supports
  • the render function then leverages this.t.reveal which will print the text in its place, defaulting to en

From the code above:

      context: this,
      basePath: import.meta.url,
      locales: ["en-UK", "ja"],
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We can see that the self-check element supports English, British English (so dialect within a language), and Japanese. The locales + basePath imply that there are JSON files located in a pattern of {pathToThisElement}/locales/{tagName}.{lang}.json and then data found there is injected back into this element when language changes. This causes the this.t object to be updated, which in turn causes the element to reflect the update.


  "reveal": "答えを明らかにする",
  "close": "閉じる",
  "more": "詳細"
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This integration has LitElement in mind and while the mixin is vanilla, it's making some assumptions about LitElement obviously via the this.t as t is supplies as an Object in the properties getter. However, this can work with 0 dependencies as the main thing happening in this Mixin is simply sending an event!

zero dependency integration

Here's all you need to work with i18n-manager:

constructor() {
  this.t = {
    whatever: "Whatever"
      new CustomEvent("i18n-manager-register-element", {
        detail: {
          context: this,
          namespace: "simple-login",
            new URL('../locales', import.meta.url).href,
          updateCallback: "render",
          locales: ["es"],
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uhh... how'd you do that!?

This supplies a context this, namespace (name of the element), a resolved localesPath based on loaded file location on the front end, an updateCallback (saying to run render on variable change), and then a locales Array.

Then it all magically works because, Magic.

No really, how we made that work

This works because we've adopted a Singleton pattern; meaning that we have a single web component that sits in the DOM and is in charge of a single concept of state management. In this case, i18n-manager is in charge of JUST translation. Who cares about translation, what translations are supplied, what the language currently is, and who to notify when language changes.

The next post will go a bit into how i18n-manager's internals are constructed and lead into a video stepping through the whole process described in these posts.

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