6.0.9 • Public • Published

Supporting Legacy Browsers

Element Framework (EF) is built on top of Lit framework and published as ES2020. The features are supported by latest versions of all modern browsers and build tools.

For legacy browsers, such as IE11 or old Chrome, it is required to compile code to ES5 and include polyfills. Lit has provided documentation for better understanding of the topic.

This guideline does not provide definite instructions to make your application working in old browsers, but rather focuses on essential information related to EF.

Legacy browsers require the following features:

  • Polyfills for Web Components
  • Convert ES2020 syntax into ES5
  • Polyfills for ES2020
  • Polyfills for i18n

Polyfills for Web Components

EF is built using Web Components standards. Old browsers may not support Web Components natively, therefore polyfills are required. EF curates necessary polyfills as @refinitiv-ui/polyfills.

npm install @refinitiv-ui/polyfills

You must import this module in your app before any EF components.

import '@refinitiv-ui/polyfills';

Convert ES2020 syntax into ES5

EF components are published using ES2020 syntax and many old browsers do not support it. Babel is popular tools to convert modern JavaScript to ES5.

npm install @babel/core --save-dev

Create or edit .browserslistrc at your application root directory to include environments that you need to support. See more about browserslist. For instance, if your application need to support IE11 add this line:

IE >= 11

Configure your build tool, to include these modules into Babel compilation list:

  • @refinitiv-ui
  • @webcomponents
  • @lit
  • lit
  • lit-element
  • lit-html
  • d3-color
  • lightweight-charts

The new versions of other dependencies might be published as modules in the future. Includes them if that is the case.

Polyfills for ES2020

Old browsers do not support many features of ES2020. core-js is a standard library that includes polyfills for ES2020+:

While you can manually include core-js polyfills, we recommend to use @babel/preset-env to automatically inject required polyfills based on your code and supported environments.

npm install core-js
npm install @babel/preset-env --save-dev

This is the minimum configuration for @babel/preset-env:

  "corejs": {
    "version": 3,
    "proposals": true
  "useBuiltIns": "usage"

Polyfills for i18n

Some EF components use Intl features, which may not be available in old browsers so the polyfills are required.

These polyfills significantly increase the size of the bundle. We recommend to only include the supported languages.

npm install @formatjs/intl-getcanonicallocales @formatjs/intl-locale @formatjs/intl-numberformat @formatjs/intl-pluralrules @formatjs/intl-datetimeformat

Import polyfills into your app:

// Import polyfills required by specific element
import '@formatjs/intl-datetimeformat/locale-data/en';
import '@formatjs/intl-datetimeformat/polyfill.iife';
import '@formatjs/intl-getcanonicallocales/polyfill.iife';
import '@formatjs/intl-locale/polyfill.iife';
import '@formatjs/intl-numberformat/locale-data/en';
import '@formatjs/intl-numberformat/polyfill.iife';
// Import supported locales, for instance `en`
import '@formatjs/intl-pluralrules/locale-data/en';
import '@formatjs/intl-pluralrules/polyfill.iife';

There are additional polyfills available for more advanced translation messages. You can get additional information on formatjs.io.

Configuration examples

Webpack 5

Webpack uses babel-loader to transpile JavaScript.

Install babel-loader and other necessary dependencies.

npm install core-js
npm install babel-loader @babel/core @babel/preset-env --save-dev

Create or edit .browserslistrc at your app root directory as per instructions in the previous section.

Merge this configuration with your WebPack configuration:

module.exports = {
  // Ensure that the output is targeted ES5 format
  target: ['web', 'es5'],
  module: {
    rules: [
        test: /\.m?js$/,
        include: [
          // Do not forget to include own project if modern JavaScript us used
          path.resolve(__dirname, 'src'),
          // Include packages that must be transpiled
          path.resolve(__dirname, 'node_modules/@refinitiv-ui'),
          path.resolve(__dirname, 'node_modules/@webcomponents'),
          path.resolve(__dirname, 'node_modules/@lit'),
          path.resolve(__dirname, 'node_modules/lit'),
          path.resolve(__dirname, 'node_modules/lit-element'),
          path.resolve(__dirname, 'node_modules/lit-html'),
          path.resolve(__dirname, 'node_modules/d3-color'),
          path.resolve(__dirname, 'node_modules/lightweight-charts')
        use: {
          loader: 'babel-loader',
          options: {
            presets: [
                  corejs: {
                    version: 3,
                    proposals: true
                  useBuiltIns: 'usage'




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npm i @refinitiv-ui/polyfills

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