ReadMeFeed / Community knowledge
Real questions. Useful conversations. Find the people who know your stack.
Developer tools · #babel
A project using @babel/preset-env must decide between useBuiltIns: 'usage' and useBuiltIns: 'entry' to control polyfill inclusion for browsers listed in the target configuration. The goal is to limit JavaScript payload while ensuring that runtime features required by the application's user-facing components are available across supported environments. The '
The goal is to determine why a Babel configuration that compiles correctly in a local development environment produces incorrect or missing transforms when executed in a production build. Key constraints involve potential differences in Babel version, browserlist target mappings, plugin ordering across combined presets, and the impact of minification on sour
Goal: select the @babel/preset-env useBuiltIns mode that keeps polyfill payload small for a low-traffic serverless function without risking missing polyfills in production. The project uses Babel 7 and declares target environments in browserslist . Constraint: usage injects only polyfills detected as used per file, usually reducing bundle size, but it can mi
Goal Determine whether a Babel-only pipeline using @babel/preset-typescript on Babel 7 guarantees type-safe JavaScript output or requires a separate TypeScript type-check step before release. Constraints Babel erases TypeScript annotations without static type checking and does not validate type compatibility across imports. It may also resolve tsconfig path
Context We are upgrading a component library (consumed by several internal apps) from core-js 2 to core-js 3. The major version change reorganized the import paths — our existing core-js/fn/array/from style specifiers no longer resolve, and the documented replacements are prefixed entry points such as /es/ , /stable/ , /features/ , and /stage/ . The unresolv
After a Babel major-version upgrade, project configuration files such as .babelrc or babel.config.js may reference presets or plugins whose APIs change, causing compilation errors or silent semantic shifts. The recovery decision hinges on two documented CLI mechanisms: --no-babelrc forces Babel to ignore project configuration and default to built-in presets,
Low-traffic polyfill loading strategy for core-js For low-traffic web applications, the choice between Babel's useBuiltIns: entry and dynamic import() polyfill loading presents a trade-off between bundle size and runtime behavior. The useBuiltIns: entry approach statically analyzes code to include only required polyfills, reducing initial payload. However, d
Context For a low‑traffic web app, every kilobyte of JavaScript counts. Core‑JS 3 offers selective imports (e.g., import 'core-js/modules/es.array.flat'; ) and a runtime detector ( import 'core-js/actual'; ) that can trim polyfills. Babel’s useBuiltIns: "usage" automatically injects only the polyfills that the target browsers actually need. However, Core‑JS
When compiling a project with @babel/preset-env , the resulting bundle runs in Node 10 and throws ReferenceError: Promise is not defined . The Babel configuration is Babel 7.12, preset‑env targets es2015 , corejs is set to 3 , but useBuiltIns is omitted. The build is produced with babel-cli and executed in an older runtime. The error suggests a missing polyf
typescript
corejs
webpack