type-fest

r https://github.com/szmarczak/http-timer https://github.com/szmarczak/defer-to-connect https://github.com/szmarczak/cacheable-lookup https://github.com/jaredwray/cacheable https://github.com/biomejs/biome https://github.com/sindresorhus/decompress-response https://github.com/sindresorhus/mimic-response https://github.com/octet-stream/form-data-encoder https://github.com/szmarczak/http2-wrapper https://github.com/szmarczak/resolve-alpn https://github.com/sindresorhus/lowercase-keys https://github.com/sindresorhus/p-cancelable https://github.com/sindresorhus/responselike https://github.com/sindresorhus/type-fest https://github.com/sindresorhus/tagged-tag https://github.com/max-mapper/extract-zip https://github.com/sindresorhus/get-stream https://github.com/Sec-ant/readable-stream https://github.com/sindresorhus/is-stream https://github.com/thejoshwolfe/yauzl https://github.com/brianloveswords/buffer-crc32 https://github.com/andrewrk/node-pend https://github.com/i18next/i18next https://github.com/babel/babel https://github.com/microsoft/TypeScript https://github.com/lezer-parser https://github.com/lucide-icons/lucide https://github.com/mathjax/MathJax https://github.com/mermaid-js/mermaid https://github.com/moment/moment https://github.com/mozilla/pdf.js https://github.com/pixijs/pixijs https://github.com/mapbox/earcut https://github.com/primus/eventemitter3 https://github.com/matt-way/gifuct-js https://github.com/matt-way/jsBinarySchemaParser https://github.com/kaimallea/isMobile https://github.com/browserslist/caniuse-lite https://github.com/jkroso/parse-svg-path https://github.com/avoidwork/tiny-lru https://github.com/PrismJS/prism/ https://github.com/mourner/rbush https://github.com/mourner/quickselect https://github.com/remarkjs/remark https://github.com/hakimel/reveal.js https://github.com/barrysteyn/node-scrypt https://github.com/nodejs/nan https://github.com/mixmark-io/turndown https://github.com/mixmark-io/domino https://github.com/webpack/webpack https://github.com/acornjs/acorn https://github.com/nicolo-ribaudo/acorn-import-phases https://github.com/browserslist/browserslist https://github.com/web-platform-dx/baseline-browser-mapping https://github.com/kilian/electron-to-chromium https://github.com/chicoxyzzy/node-releases https://github.com/browserslist/update-db https://github.com/lukeed/escalade https://github.com/alexeyraspopov/picocolors https://github.com/samccone/chrome-trace-event https://github.com/webpack/enhanced-resolve https://github.com/isaacs/node-graceful-fs https://github.com/webpack/tapable https://github.com/guybedford/es-module-lexer https://github.com/eslint/js https://github.com/browserify/events https://github.com/fitzgen/glob-to-regexp https://github.com/isaacs/node-graceful-fs https://github.com/npm/json-parse-even-better-errors https://github.com/webpack/loader-runner https://github.com/jshttp/mime-types https://github.com/jshttp/mime-db https://github.com/suguru03/neo-async https://github.com/webpack/schema-utils https://github.com/ajv-validator/ajv https://github.com/epoberezkin/fast-deep-equal https://github.com/fastify/fast-uri https://github.com/epoberezkin/json-schema-traverse https://github.com/floatdrop/require-from-string https://github.com/ajv-validator/ajv-formats https://github.com/ajv-validator/ajv-keywords https://github.com/DefinitelyTyped/DefinitelyTyped https://github.com/webpack-contrib/terser-webpack-plugin https://github.com/jridgewell/sourcemaps https://github.com/jestjs/jest https://github.com/yahoo/serialize-javascript https://github.com/browserify/randombytes https://github.com/terser/terser https://github.com/tj/commander.js https://github.com/evanw/node-source-map-support https://github.com/LinusU/buffer-from https://github.com/mozilla/source-map https://github.com/webpack/watchpack https://github.com/webpack/webpack-sources https://github.com/eemeli/yaml

y (your `tag` is also there at runtime) 5. Can be composed, like this: type Url = Tagged<string, 'URL'>; type SpecialCacheKey = Tagged<Url, 'SpecialCacheKey'>; See my other comment for more on what a complete branded type offers https://news.ycombinator.com/item?id=40368052 [0] https://github.com/sindresorhus/type-fest/blob/main/source/o... [1] https://www.typescriptlang.org/play/?#code/C4TwDgpgBAEghgZwB...

o a user id from your DB can be a `UserId`, a `ModeratorId`, an `AdminId` and a plain string (when actually sending it to a raw DB method) as needed. Try doing this (playground in [1]) with template literals: type UserId = Tagged<string, 'UserId'> type ModeratorId = Tagged<UserId, 'ModeratorId'> // notice we composed with UserId here type AdminId = Tagged<UserId, 'AdminId'> // and here const banUser = (banned: UserId, banner: AdminId) => { console.log(`${banner} just banned ${banned.toUpperCase()}`) } const notifyUser = (banned: UserId, notifier: ModeratorId) => { console.log(`${notifier} just notified ${banned.toUpperCase()}`) // notice toUpperCase here } const banUserAndNotify = (banned: UserId, banner: ModeratorId & AdminId) => { banUser(banned, banner) notifyUser(banned, banner) } const getUserId = () => `${Math.random().toString(16)}` as UserId const getModeratorId = () => // moderators are also users! // but we didn't need to tell it explicitly here with `as UserId & ModeratorId` (we could have though) `${Math.random().toString(16)}` as ModeratorId const getAdminId = () => // just like admins are also users `${Math.random().toString(16)}` as AdminId const getModeratorAndAdminId = () => // this is user is BOTH moderator AND admin (and a regular user, of course) // note here we did use the `&` type intersection `${Math.random().toString(16)}` as ModeratorId & AdminId banUser(getUserId(), getAdminId()) banUserAndNotify(getUserId(), getAdminId()) // this fails banUserAndNotify(getUserId(), getModeratorId()) // this fails too banUserAndNotify(getUserId(), getModeratorAndAdminId()) // but this works banUser(getAdminId(), getAdminId()) // you can even ban admins, because they're also users console.log(getAdminId().toUpperCase()) // this also works getAdminId().toUpperCase() satisfies string // because of this banUser(getUserId(), getAdminId().toUpperCase()) // but this fails (as it should) getAdminId().toUpperCase() satisfies AdminId // because this also fails You can also do stuff like: const superBan = <T extends UserId>(banned: Exclude<T, AdminId>, banner: AdminId) => { console.log(`${banner} just super-banned ${banned.toUpperCase()}`) } superBan(getUserId(), getAdminId()) // this works superBan(getModeratorId(), getAdminId()) // this works too superBan(getAdminId(), getAdminId()) // you cannot super-ban admins, even though they're also users! [0] https://github.com/sindresorhus/type-fest/blob/main/source/o... [1] https://www.typescriptlang.org/play/?#code/CYUwxgNghgTiAEYD2...

nd up in situations where nobody even _really_ understands why some crazy type works. [0]: https://github.com/sindresorhus/type-fest/blob/2f418dbbb6182...