JsonAccess — simple type-safe access to JSON for Typescript

Receiving some string text from an API which is supposedly JSON with a given structure, we want to parse the JSON and if this does not fail, access the resulting structured data in a typesafe manner.

Consider an API which is expected to deliver a tuple with type:

[string, number]

and we want to savely access the values to create an Item:

 const data = jsonParse(text);
 type Item = { id: string; price: number };
 const item: Maybe<Item> = jsonAsType(
 data,
 [jsonStringGetter('item'), jsonNumberGetter('price')],
 (i, p) => ({ item: i, price: p })
 );
 if (!isValid(item)) {
 throw item; // a JsonAccessError
 }
 // continue with item properly typed as Item

For more information see the api documentation.

Setup

To install the package, follow the instruction on codeberg's package page.

Alternatives

TypeScript-first schema validation with static type inference: zod