JSDoc to TypeScript Converter

Why promote JSDoc types to TypeScript?

JSDoc is a strong convention, but it has real limitations: types live in comments, tooling support varies between editors, and nothing guarantees comments stay in sync with code. TypeScript gives you the same type expressiveness with compiler-enforced correctness, first-class refactoring, and better IDE intelligence.

If you've already done the work to document functions with JSDoc, JavaScriptConverter extracts that information and turns it into real TypeScript annotations automatically. Nothing is lost, and the compiler starts checking your types immediately.

JSDoc patterns this tool understands

/**
 * @param {string} name
 * @param {number} [age]
 * @returns {string}
 */
function greet(name, age) {
  return 'Hello ' + name;
}

function greet(
  name: string,
  age?: number
): string {
  return 'Hello ' + name;
}

/** @type {Array<string>} */
const names = [];

const names: Array<string> = [];

/**
 * @param {string|number} id
 */
function find(id) { /* ... */ }

function find(id: string | number) {
  /* ... */
}

What happens to parameters without JSDoc?

Parameters without JSDoc are left with TypeScript's implicit any (or explicit unknown if you enable strict mode). The converter never invents types it can't justify — unlike LLM-based tools, you get exactly what was documented and nothing more. This gives you a reliable starting point to tighten types incrementally.