Consuming generics in Javascript

[wenq1]

Suggestion

Currently javascript cannot consume typescript generic functions, resulting in warnings ts(2339) in ReactDom's useParams ().

Prototype in .d.ts file:

export function useParams<Params extends { [K in keyof Params]?: string } = {}>(): Params;

Consumption in javascript:

   const   { mode = 'default' } = useParams ();
                  ^ Property 'mode' does not exist on type '{}'. ts(2339)

🔍 Search Terms

javascript consume generics

✅ Viability Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, new syntax sugar for JS, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

⭐ Suggestion

It is currently possible to do something like this in javascript:

/**
 * @typedef {{mode: string, mode2: string}} TestParams
 */

   const   { mode = 'default' }  = /** @type { () => TestParams } */ (useParams) ();

Is there a way to do something like this instead?

   const   { mode = 'default' }  = /** @useTemplate <TestParams> */ (useParams) ();

📃 Motivating Example

💻 Use Cases

See above

Also found #27387

[RyanCavanaugh]

Same as #27387