TS2304: Cannot find name 'X'

Common causes

• Forgot to import the variable, type, or function from another file
• A typo in the name — TypeScript is case-sensitive
• Using a browser global (window, document) without the dom lib in tsconfig.json
• Using a type from a library that needs its @types package installed

How to fix it

1. Import the missing name: import { MyClass } from './myModule'
2. Declare it if it's a local variable you forgot: const myVar = ...
3. Add the appropriate lib to tsconfig.json: "lib": ["dom", "es2020"] for browser globals
4. Install the @types package: npm install --save-dev @types/node for Node.js globals like process

Example

Referencing a variable that hasn't been declared or imported in the current scope