Internet Explorer 11 is a fixed compatibility target: it lacks Web Components, Shadow DOM, and ES2015 features such as classes and arrow functions. Supporting it requires older JavaScript output and browser-specific fallbacks. section 12.5 section 2.7
A practical IE11 support path combines:
- Babel with @babel/core, @babel/cli, and @babel/preset-env to transpile modern JavaScript into older JavaScript. section 12.5
- The custom-elements polyfill to provide Custom Elements support. section 2.7
- A CSS variables ponyfill when existing component styles depend on CSS custom properties. section 12.5
- Shadow DOM disabled or adapted, because its CSS behavior cannot be fully polyfilled in IE. section 10.4
Separate modern and IE builds
Bundle components for modern browsers, then run Babel on each generated component file. A combined npm script such as "build-ie" produces slider.build.js, coordpicker.build.js, and colorpicker.build.js for IE11. Load the transpiled script instead of the module entry point, and include the required polyfills before it. section 12.5
npm install --save-dev @babel/core npm install --save-dev @babel/cli npm install --save-dev @babel/preset-env
Use the installation commands to begin configuring Babel as development-only build tooling. section 12.5
