TypeScript errorTypeScript: “Cannot find name 'x'” (TS2304, TS2580, TS2582, TS2591)

Why TypeScript can’t see the name, and the fix

1. 01

   The Node.js types are not installed

   “Definitions on DefinitelyTyped are also automatically published to npm under the @types scope.” TypeScript, Type declarations: DefinitelyTyped

   process, require, module, Buffer and __dirname come from Node.js, not from JavaScript itself, so TypeScript needs the Node.js type package to know them. On TypeScript 6 or later, also add "node" to types in tsconfig.json.

   npm install --save-dev @types/node

2. 02

   A types list in tsconfig leaves the package out

   “If types is specified, only packages listed will be included in the global scope.” TypeScript, TSConfig reference: types

   Before TypeScript 6.0, every installed @types package loaded when types was not set. From 6.0 the default is an empty list, so you list the packages you need. Either way, once types is set only those load, so a package you just installed stays invisible until you add it.

   {
     "compilerOptions": {
       "types": ["node", "jest"]
     }
   }

3. 03

   Test globals: describe, it, expect

   Jest and Vitest add describe, it and expect as globals at runtime, but TypeScript only knows them from the runner’s types. For Jest install @types/jest. For Vitest, either import them from vitest in each file, or set globals: true in the Vitest config and add "vitest/globals" to types.

   // Vitest, per file
   import { describe, it, expect } from 'vitest';
   
   // or tsconfig.json with globals: true
   "types": ["vitest/globals"]

4. 04

   document or window in a project without the DOM library

   A lib setting in tsconfig.json without "DOM" removes browser globals such as document, window and fetch types. Add it for browser code. If the code really runs on a server, the error is right: move that code to the browser side.

   {
     "compilerOptions": {
       "lib": ["ES2022", "DOM", "DOM.Iterable"]
     }
   }

Checked against the vendor’s docs on November 8, 2026: TypeScript: TSConfig reference (types, lib); TypeScript Handbook: Type declarations.

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Related: TypeScript “Property does not exist on type” · TypeScript “Type is not assignable to type” · “require is not defined”