Choosing core-js polyfills: full bundle or targeted imports
Decide between full core-js, modular feature imports, and Babel usage-based polyfills based on bundle size and target browsers.
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Developer tools · #corejs
Use core-js v3 stable to polyfill finished ECMAScript APIs for legacy browsers
Add runtime polyfills for finished ECMAScript features with core-js v3 stable while keeping syntax transforms separate.
Ship fewer core-js polyfills by matching imports to your browser targets
Stop shipping every core-js polyfill to every browser. Use core-js-compat with browserslist to import only the ECMAScript polyfills your supported targets actually need.
Polyfilling Array.prototype.flatMap with core-js: A Step‑by‑Step Guide for Legacy Browser Support
Add Array.prototype.flatMap support to legacy browsers with core-js. Follow this guide to install, import, and verify the polyfill while keeping bundle size and performance in check.
Load only the CoreJS optional-chaining polyfill you need
Use selective core-js imports to add optional chaining to older browsers without shipping the full standard library.
Stop importing all of core-js: targeted polyfills with feature detection
Blanket core-js imports bloat bundles and risk overriding natives. Targeted modular imports with runtime feature detection give smaller builds and safer polyfills for web and Node apps.
Stop Shipping the Whole core-js Library: Use Modular Polyfill Imports
Stop shipping every core-js polyfill. Import only the ECMAScript features your app uses and verify the savings in your production bundle.
Adding the Array.prototype.flat polyfill from core-js for legacy browsers
Import only the Array.flat polyfill from core-js to support IE11 and Safari 10 without bloating your JavaScript bundle.
Handling Legacy Environments with CoreJS Object.fromEntries
Stop using .reduce() to build objects from maps. Learn how to implement the ES2020 Object.fromEntries polyfill via CoreJS to ensure cross-browser compatibility without bloating your bundle.