core-js-builder

I highly recommend reading this: So, what's next?

For some cases could be useful to exclude some core-js features or generate a polyfill for target engines. This API helps conditionally include or exclude certain parts of core-js and build for targets. modules, exclude and targets options are specified in the core-js-compat format.

import builder from 'core-js-builder';

const bundle = await builder({
  // entry / module / namespace / an array of them, by default - all `core-js` modules
  modules: ['core-js/actual', /^esnext\.reflect\./],
  // a blacklist of entries / modules / namespaces, by default - empty list
  exclude: [/^es\.math\./, 'es.number.constructor'],
  // optional browserslist or core-js-compat format query
  targets: '> 0.5%, not dead, ie 9-11',
  // shows summary for the bundle, disabled by default
  summary: {
    // in the console, you could specify required parts or set `true` for enable all of them
    console: { size: true, modules: false },
    // in the comment in the target file, similarly to `summary.console`
    comment: { size: false, modules: true },
  },
  // output format, 'bundle' by default, can be 'cjs' or 'esm', and in this case
  // the result will not be bundled and will contain imports of required modules
  format: 'bundle',
  // optional target filename, if it's missed a file will not be created
  filename: PATH_TO_MY_COREJS_BUNDLE,
});

ℹ️ When using TypeScript, make sure to set esModuleInterop to true.

Changelog

3.42.0 - 2025.04.30

• Changes v3.41.0...v3.42.0 (142 commits)
• Map upsert proposal:
  • Moved to stage 2.7, April 2025 TC39 meeting
  • Validation order of WeakMap.prototype.getOrInsertComputed updated following tc39/proposal-upsert#79
  • Built-ins:
    • Map.prototype.getOrInsert
    • Map.prototype.getOrInsertComputed
    • WeakMap.prototype.getOrInsert
    • WeakMap.prototype.getOrInsertComputed
• Don't call well-known Symbol methods for RegExp on primitive values following tc39/ecma262#3009:
  • For avoid performance regression, temporarily, only in own core-js implementations
  • Built-ins:
    • String.prototype.matchAll
    • String.prototype.match
    • String.prototype.replaceAll
    • String.prototype.replace
    • String.prototype.search
    • String.prototype.split
• Added workaround for the Uint8Array.prototype.setFromBase64 bug in some of Linux builds of WebKit
• Implemented early-error iterator closing following tc39/ecma262#3467, including fix of a WebKit bug, in the following methods:
  • Iterator.prototype.drop
  • Iterator.prototype.every
  • Iterator.prototype.filter
  • Iterator.prototype.find
  • Iterator.prototype.flatMap
  • Iterator.prototype.forEach
  • Iterator.prototype.map
  • Iterator.prototype.reduce
  • Iterator.prototype.some
  • Iterator.prototype.take
• Fixed missing forced replacement of AsyncIterator helpers
• Added closing of sync iterator when async wrapper yields a rejection following tc39/ecma262#2600. Affected methods:
  • Array.fromAsync (due to the lack of async feature detection capability - temporarily, only in own core-js implementation)
  • AsyncIterator.from
  • Iterator.prototype.toAsync
• Added detection for throwing on undefined initial parameter in Iterator.prototype.reduce (see WebKit bug)
• core-js-compat and core-js-builder API:
  • Added 'intersect' support for targets.esmodules (Babel 7 behavior)
  • Fixed handling of targets.esmodules: true (Babel 7 behavior)
• Compat data improvements:
  • Explicit Resource Management features disabled (again) in V8 ~ Chromium 135 and re-added in 136
  • RegExp.escape marked as shipped from V8 ~ Chromium 136
  • Error.isError marked as shipped from FF138
  • Explicit Resource Management features re-enabled in Deno 2.2.10
  • Iterator helpers proposal features marked as supported from Deno 1.38.1 since it seems they were disabled in 1.38.0
  • Iterator.prototype.{ drop, reduce, take } methods marked as fixed in Bun 1.2.11
  • Added NodeJS 24.0 compat data mapping
  • Updated Electron 36 and added Electron 37 compat data mapping
  • Added Opera Android 88 and 89 compat data mapping
  • Added Oculus Quest Browser 37 compat data mapping