Runtime data validation for TypeScript

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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.

typescript validation
1 Answers

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).

user_26416320
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