TypeScript has no runtime check to ensure that loaded data matches the types. We currently use JSON schemas that we generate from our types with typescript-json-schema via a CLI and then validate in runtime with ajv. A great solution we thought until we found that it didn't play well with JS dates since dates are not part of JSON.
Does anyone have a solution for this? We use types not classes.
You can use zod library. You will only need to have one schema and you can use it to generate types & validate data using JSON Schema.
Zod is a TypeScript-first schema declaration and validation library. I'm using the term "schema" to broadly refer to any data type/structure, from a simple string to a complex nested object.
Take a look at this example:
import * as z from 'zod'
const schema = z.object({
stringValue: z.string(),
numberValue: z.number(),
dateValue: z.date()
})
type MyType = z.infer<typeof schema>
// type MyType = {
// stringValue: string;
// numberValue: number;
// dateValue: Date;
// }
const data = schema.parse({
stringValue: 'Hello',
numberValue: 1,
dateValue: new Date()
})
The biggest issue with this library is that it doesn't work well when you need to transform data (e.g. you get the date as a string). It has an open issue regarding data transformation. Also, you can't generate JSON schema from zod instance (check the issue).
Zod 3 resolved data transformation
