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Declare a type with a JSON file instead of an interface #23898
Description
Activity
You are in luck! #22167 just got merged, and with
--resolveJsonModuleyou can load the json object in your program and use its type..with
importtypes too you can capture that type in a type alias:type schemaType = typeof import("./schema.json");
nice that is cool, how do we know when the next
tscversion will be published on NPM? is there some notification system?It is published nightly around midnight PST
Automatically closing this issue for housekeeping purposes. The issue labels indicate that it is unactionable at the moment or has already been addressed.
Mohamed Hegazy (@mhegazy) one potential improvement!
tsc can now use .json files for types - but can
tscuse json-schema files to determine generic types?for example, say I have this JSON file:
{ "foo":"bar" }now, foo the interface for the above could be:
interface JSON { foo: "bar" }or it could be:
interface JSON { foo: string }which does
tsccurrently do? Couldtscbe updated to handle json-schema from
http://json-schema.org/?
Reacted by Veaceslav Cotruta and Marcus OtterströmMohamed Hegazy (@mhegazy) what about importing json files and getting type info? If I do:
import json = require('../../my.json')
and also use:
"resolveJsonModule": true,in my tsconfig.json. My project no longer compiles correctly. Is this a known problem? Should I file a new ticket?
Should I file a new ticket?
yes please.
Mohamed Hegazy (@mhegazy) thanks, I filed the issue here: #25216
- locked as resolved and limited conversation to collaborators
on Oct 21, 2025
Search Terms
typescript json interface file
Suggestion
I have this question on SO:
https://stackoverflow.com/questions/50181254/static-typing-with-json-and-typescript?noredirect=1#comment87380729_50181254
Why can't we declare a TS type based on a .json file? Something like this:
it seems like a no-brainer to me, but maybe I am stupid.
Use Cases
Keep things DRY. Use JSON files as interfaces.
Examples
Done did.
Checklist
My suggestion meets these guidelines:
[x] This wouldn't be a breaking change in existing TypeScript / JavaScript code
[x] This wouldn't change the runtime behavior of existing JavaScript code
[x] This could be implemented without emitting different JS based on the types of the expressions
[x] This isn't a runtime feature (e.g. new expression-level syntax)