--- title: "TypeScript 6.0: the bridge release before the Go compiler · vuejs.school" description: "TypeScript 6.0 is the last release on the JavaScript codebase. It changes defaults and deprecates old options ahead of 7.0. Here is what a Vue project must fix." canonical_url: "https://vuejs.school/community/blog/typescript-6-the-bridge-release" meta: "og:description": "TypeScript 6.0 is the last release on the JavaScript codebase. It changes defaults and deprecates old options ahead of 7.0. Here is what a Vue project must fix." "og:image": "https://vuejs.school/_og/d/a_~VHlwZVNjcmlwdCA2LjA6IHRoZSBicmlkZ2UgcmVsZWFzZSBiZWZvcmUgdGhlIEdvIGNvbXBpbGVyIMK3IHZ1ZWpzLnNjaG9vbA%2Cc_OgCard.takumi%2Ctitle_~VHlwZVNjcmlwdCA2LjA6IHRoZSBicmlkZ2UgcmVsZWFzZSBiZWZvcmUgdGhlIEdvIGNvbXBpbGVy%2Cdescription_TypeScript%2B6.0%2Bis%2Bthe%2Blast%2Brelease%2Bon%2Bthe%2BJavaScript%2Bcodebase.%2BIt%2Bchanges%2Bdefaults%2Band%2Bdeprecates%2Bold%2Boptions%2Bahead%2Bof%2B7.0.%2BHere%2Bis%2Bwhat%2Ba%2BVue%2Bproject%2Bmust%2Bfix.%2Ceyebrow_~UmVsZWFzZSBub3RlcyDCtyA3IG1pbiByZWFk%2Ctint_sky%2Cp_Ii9jb21tdW5pdHkvYmxvZy90eXBlc2NyaXB0LTYtdGhlLWJyaWRnZS1yZWxlYXNlIg%2Cs_9-6U1XMD87LFlLV8.png" "og:image:alt": "TypeScript 6.0: the bridge release before the Go compiler · vuejs.school" "og:image:height": "600" "og:image:type": image/png "og:image:width": "1200" "og:title": "TypeScript 6.0: the bridge release before the Go compiler · vuejs.school" "twitter:image": "https://vuejs.school/_og/d/a_~VHlwZVNjcmlwdCA2LjA6IHRoZSBicmlkZ2UgcmVsZWFzZSBiZWZvcmUgdGhlIEdvIGNvbXBpbGVyIMK3IHZ1ZWpzLnNjaG9vbA%2Cc_OgCard.takumi%2Ctitle_~VHlwZVNjcmlwdCA2LjA6IHRoZSBicmlkZ2UgcmVsZWFzZSBiZWZvcmUgdGhlIEdvIGNvbXBpbGVy%2Cdescription_TypeScript%2B6.0%2Bis%2Bthe%2Blast%2Brelease%2Bon%2Bthe%2BJavaScript%2Bcodebase.%2BIt%2Bchanges%2Bdefaults%2Band%2Bdeprecates%2Bold%2Boptions%2Bahead%2Bof%2B7.0.%2BHere%2Bis%2Bwhat%2Ba%2BVue%2Bproject%2Bmust%2Bfix.%2Ceyebrow_~UmVsZWFzZSBub3RlcyDCtyA3IG1pbiByZWFk%2Ctint_sky%2Cp_Ii9jb21tdW5pdHkvYmxvZy90eXBlc2NyaXB0LTYtdGhlLWJyaWRnZS1yZWxlYXNlIg%2Cs_9-6U1XMD87LFlLV8.png" "twitter:image:alt": "TypeScript 6.0: the bridge release before the Go compiler · vuejs.school" --- > Index of every page on this site: [llms.txt](https://vuejs.school/llms.txt) ## Why 6.0 is a bridge release The TypeScript team is porting the compiler and language service to Go, for the speed of native code and for shared-memory multi-threading. That new codebase becomes TypeScript 7.0, while 6.0 stays on the JavaScript one. The tool 6.0 uses to prepare you is deprecation. Options that 7.0 will not support now raise an error in 6.0. You can silence those errors by adding `"ignoreDeprecations": "6.0"` to your `tsconfig.json`, but the announcement is plain that 7.0 will not support any of the deprecated options. ## The new defaults Several options have a new default value. If your `tsconfig.json` already sets an option, the new default does not affect you. The changes: - `strict` is now `true`. - `module` defaults to `esnext`. - `target` defaults to the newest ECMAScript version TypeScript supports, which is `es2025` in this release. - `noUncheckedSideEffectImports` is now `true`. An import with no bindings, such as `import './assets/main.css'`, must resolve to something TypeScript knows about. - `libReplacement` is now `false`. TypeScript no longer searches `node_modules` for packages that replace its built-in `lib` files, a search that cost time on every run and found nothing unless you had set such a package up. - `rootDir` defaults to the folder that contains `tsconfig.json`, instead of being worked out from your source files. - `types` defaults to `[]`, so TypeScript no longer loads every package in `node_modules/@types` on its own. The announcement reports builds 20 to 50 percent faster in projects that set `types` properly. The last two are the ones the announcement warns about. Many projects will need `"types": ["node"]`, it says, and projects whose output lands in `dist/src/` instead of `dist/` need `"rootDir": "./src"`. ## The deprecated and removed options These now raise an error unless silenced: - `target: "es5"`, since the lowest target is now ES2015, and `downlevelIteration`, which only affected ES5 output. - `moduleResolution: "node"` (also called `node10`) and `moduleResolution: "classic"`. Use `bundler` for code that goes through Vite and `nodenext` for code that Node runs directly. - `module` set to `amd`, `umd`, `systemjs` or `none`. - `baseUrl`. Aliases in `paths` have not needed it for years, and it also made TypeScript resolve bare imports from that folder, which hid imports that would fail at runtime. - `esModuleInterop: false` and `allowSyntheticDefaultImports: false`. The safer interop is always on now. - `alwaysStrict: false`. All code is treated as JavaScript strict mode. - `outFile`. Concatenating files is a bundler's job. Two old syntax forms are now errors: - `module Foo {}` for a namespace. Write `namespace Foo {}`. A `declare module '*.vue'` block, whose name is in quotes, is not affected. - Import assertions written `assert { type: 'json' }`. Write `with { type: 'json' }`. On the command line, running `tsc somefile.ts` in a folder that has a `tsconfig.json` is now error TS5112, because the config used to be ignored without a word. Add `--ignoreConfig` if ignoring it is what you want. ## New features you can use Alongside the deprecations, the release adds: - `"lib": ["dom"]` now contains what `dom.iterable` and `dom.asynciterable` held, so `for (const li of document.querySelectorAll('li'))` type-checks without the extra entries. - An `es2025` value for `target` and `lib`, with types for `RegExp.escape`. `Promise.try`, iterator helpers and the new `Set` methods move from `esnext` into `es2025`. - Types for Temporal under `esnext` or `esnext.temporal`, and for `Map.getOrInsert()` and `getOrInsertComputed()` under `esnext`. These are types only. TypeScript adds no runtime code and Vite adds no polyfills, so check browser support before using them in an app. - Subpath imports that start with `#/`, under `moduleResolution` `bundler` and `nodenext`. - `--stableTypeOrdering`, which makes 6.0 order union types the way 7.0 will. It exists to compare output between the two and can slow type checking by up to 25 percent, so it is not for everyday use. ## What a Vue project needs to change Take a project scaffolded with `npm create vue@latest`. Its `tsconfig.app.json` extends `@vue/tsconfig/tsconfig.dom.json`, which already sets `strict`, `module`, `target`, `libReplacement: false` and `types: []`. The `tsconfig.node.json` and `tsconfig.vitest.json` files list their `types` explicitly. Every config sets `noEmit`, so the `rootDir` change has nothing to act on. In a recent project the new defaults change nothing, provided `env.d.ts` is still in place (see below). Older projects differ in one place. create-vue releases before 3.12.2, published on 29 November 2024, wrote `baseUrl` into `tsconfig.app.json`: *tsconfig.app.json**Breaks*** ``` { "extends": "@vue/tsconfig/tsconfig.dom.json", "include": ["env.d.ts", "src/**/*", "src/**/*.vue"], "compilerOptions": { "baseUrl": ".", "paths": { "@/*": ["./src/*"] } } } ``` On TypeScript 6.0, `vue-tsc --build` stops with `error TS5101: Option 'baseUrl' is deprecated and will stop functioning in TypeScript 7.0. Specify compilerOption '"ignoreDeprecations": "6.0"' to silence this error.` The `paths` entry already starts with `./`, so the fix is deleting one line: *tsconfig.app.json**Works*** ``` { "extends": "@vue/tsconfig/tsconfig.dom.json", "include": ["env.d.ts", "src/**/*", "src/**/*.vue"], "compilerOptions": { "paths": { "@/*": ["./src/*"] } } } ``` Paths without `baseUrl` work on 5.9 as well, so you can land this fix before the upgrade. The second thing to check is `env.d.ts`. With `noUncheckedSideEffectImports` on, the CSS import in `src/main.ts` needs a declaration for `*.css` files. Vite ships one in its client types, and create-vue loads them in `env.d.ts`: *env.d.ts* ``` /// ``` If that file is gone, or no longer in `include`, TypeScript 6.0 reports `error TS2882: Cannot find module or type declarations for side-effect import of './assets/main.css'`. Put the reference back. A triple-slash reference like this one is not affected by the new `types` default. A project with its own hand-written `tsconfig.json` and no `types` entry meets the new `types` default. A file that uses Node's APIs, such as a script that reads `process.argv` or imports `node:fs`, now fails with `error TS2591: Cannot find name 'process'` (or `'node:fs'`). The exception is a config that also includes a file importing from `vite`, usually `vite.config.ts`: Vite's own type declarations load the Node types, and then every file in that config sees them. A config that covers only `src` gets no such help. Do not rely on Vite for this; add the Node types to `compilerOptions` yourself: *tsconfig.json* ``` { "compilerOptions": { "types": ["node"] } } ``` ## How to upgrade create-vue pins TypeScript with a tilde, `"typescript": "~5.9.3"`, which only allows 5.9 patch releases. `npm update` will never move you to 6.0, so install it by name. Update `@vue/tsconfig` in the same command: version 0.9.1, published early on 24 March, widens its peer range to TypeScript 5.8 and later, where 0.9.0 and older ask for TypeScript 5. ``` npm install -D typescript@~6.0.2 @vue/tsconfig@^0.9.1 npm run type-check ``` vue-tsc needs no update. Version 3.2.6, published on 17 March, declares any TypeScript from 5.0 up as its peer and runs on 6.0.2 as it is; the TS5101 message above is exactly what it prints. Most errors after the upgrade come from the new defaults and the deprecations above. The rest come from inference changes. Functions that never use `this` are now inferred earlier in generic calls, which fixes some errors, and checking of function expressions in generic calls was tightened after the beta, which may add some. If a generic call starts failing, give it an explicit type argument, as the announcement suggests. ## Wait if you lint with typescript-eslint If you picked both TypeScript and ESLint in create-vue, the parser that reads your `.ts` files comes from typescript-eslint, pulled in by `@vue/eslint-config-typescript`. Its latest release, 8.57.2, declares support for TypeScript `>=4.8.4 <6.0.0`. Install 6.0 next to it anyway and you get two kinds of complaint: - From npm, `ERESOLVE overriding peer dependency` warnings. If you list `typescript-eslint` directly in `package.json`, npm stops with `ERESOLVE unable to resolve dependency tree` instead. - From the parser, each time ESLint runs, a banner saying you are running a version of TypeScript that is not officially supported, with a request to file bug reports only on supported versions. Check with `npm view typescript-eslint peerDependencies`, and upgrade TypeScript once the `typescript` range in that output includes 6.0. Until then, you can still delete `baseUrl`. If your project does not lint with typescript-eslint, upgrade now: two version bumps, perhaps one deleted line, and a config with no deprecated options left for 7.0 to drop. **Check it stuck**3 questions from the Type checking and editor setup quiz. [**Practice now**](https://vuejs.school/learn/typescript/type-checking-and-editor-setup?tab=quiz) **Was this helpful?** ## **Keep reading** [Tutorial · 6 min read**TypeScript strict mode in a Vue project: the errors you'll hit and the fixes**](https://vuejs.school/community/blog/typescript-strict-mode-in-a-vue-project) [Release notes · 7 min read**TypeScript 7.0: the Go compiler lands, and what it means for vue-tsc**](https://vuejs.school/community/blog/typescript-7-the-go-compiler-lands) ```json {"@context":"https://schema.org","@graph":[{"@id":"https://vuejs.school/#website","@type":"WebSite","description":"A free AI-instructed school for Vue.js. 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