Types for Response.json() Static Method

[karlhorky]

Suggestion

🔍 Search Terms

response, responses, static method, json, Response.json()

✅ 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

Now that multiple JavaScript runtimes (Chromium, Node.js v18 LTS, Bun, etc) have implemented it, it would be great to get types for the Response.json() static method (Chrome Platform Status, Mozilla Bugzilla, Response.json() section in Fetch spec).

Since Response objects are more commonly used on the backend, maybe backend runtimes can be considered as valid signals that this is ready for inclusion in TypeScript.

📃 Motivating Example

Response.json({abc: 123}, {status: 400});

Playground

💻 Use Cases

A shortcut for the following code (more verbose / error prone):

new Response(JSON.stringify({ abc: 123 }), {
  status: 400,
  headers: {
    'Content-Type': 'application/json',
  },
});

👀 See also

This has a companion issue + PR in the microsoft/TypeScript-DOM-lib-generator repo over here:

• Add method static Response.json(data, init) TypeScript-DOM-lib-generator#1444
• introduces Response.json() static method TypeScript-DOM-lib-generator#1462

cc @lucacasonato @balazsorban44 @leerob @cramforce @jasnell

[balazsorban44]

Just pointing out that the shortcut is in fact so error prone, that you forgot to add the "Content-Type": "application/json" header. 😜

This would be a great addition! 👍

I also wanted to add this to MDN but got blocked mdn/content#22970 (comment)

[lucacasonato]

Just pointing out that the shortcut is in fact so error prone, that you forgot to add the "Content-Type": "application/json" header. 😜

Response.json automatically sets the content type header to json.

[karlhorky]

you forgot to add the "Content-Type": "application/json" header. 😜

haha indeed oops, edited the description above to add it!

[lucacasonato]

No, the header is added by Response.json already. The previous example was correct 😃

[cramforce]

@lucacasonato the comment was about the long-form non-helper version which was originally missing it. Was important to add to show that the helper does more work!

[karlhorky]

Oh nice, it looks like microsoft/TypeScript-DOM-lib-generator#1462 was merged! 🙌

@RyanCavanaugh does this mean that this issue can be closed now? (will this be a part of TypeScript in one of the next versions like 5.2?)

[RyanCavanaugh]

This would be in 5.2 as soon as we do the next regular lib update, yes. Marking closed. Thanks!

[karlhorky]

Great, thanks!