Tag: ESM

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.