When editing in VSCode, if a JS file imports ESM exports from another a node_modules library, if that library is in JS, then type declarations are required for type hinting? If the node_modules library is in TS, are type declarations required for type hinting?

Here’s a comprehensive explanation:

When a JS file imports ESM exports from a Node.modules library:

• If the library is in JS:

  • Type declarations are needed for type hinting in VS Code.
  • Methods to provide type declarations:
    1. Library-provided types:
       • Check if the library includes its own types, often in a @types or dist directory. Install them using npm or yarn.
    2. DefinitelyTyped:
       • Search for community-maintained types on DefinitelyTyped. Install using @types/<library-name>.
    3. Create manual type declarations:
       • If types aren’t available, create a .d.ts file with type definitions for the library’s exports.

• If the library is in TypeScript:

  • Type declarations are typically not required.
  • VS Code can infer types directly from the library’s TypeScript code.

Key points for optimal type hinting experience:

• Enable the TypeScript extension in VS Code.
• Configure VS Code to discover type declarations:
  • Set typeRoots in jsconfig.json or tsconfig.json to include node_modules/@types.
• Consider using a type checker for enhanced type safety and linting:
  • Explore ESLint with TypeScript plugins or standalone type checkers like TypeScript ESLint or tsc.

Additional tips:

• Keep type declarations up-to-date:
  • Ensure they match library versions for accuracy.
• Leverage VS Code’s IntelliSense for guidance:
  • Utilize code completion, hover information, and error checking for efficient coding.
• Explore advanced features:
  • Type search (Cmd+T or Ctrl+T), go to type definition (F12), type hierarchy exploration, and more.