Question 1

How do I add a custom validation rule in JJV?

Accepted Answer

Use the addCheck function to define custom validation keywords. For example, env.addCheck('exactLength', function(v, p) { return v.length === p; }) enables validating exact lengths for arrays or strings based on your schema.

Question 2

Is JJV better than Ajv for JSON schema validation?

Accepted Answer

JJV is faster for draft v4 and has no dependencies, but Ajv supports newer drafts and has a larger ecosystem. Choose JJV if you need draft v4 compliance and performance; otherwise, Ajv is more future-proof.

Question 3

Does JJV support JSON Schema draft 7?

Accepted Answer

No, JJV only implements draft v4 of the JSON Schema Core. For draft 7 or later features like conditional schemas, you'll need a different validator like Ajv or TV4.

Question 4

How to use JJV to validate API data in Node.js?

Accepted Answer

Install JJV via npm, create an environment with jjv(), register schemas using addSchema, and validate objects with env.validate(). For instance, errors = env.validate('user', data) returns null on success or an error object.

Question 5

Can JJV automatically fetch schemas from a URL?

Accepted Answer

No, JJV does not fetch remote schemas to avoid performance and security issues. You must manually register schemas locally using addSchema or load them beforehand.

Question 6

How to enable type coercion in JJV for string to number conversion?

Accepted Answer

Set the useCoerce option to true and define custom coercion rules with addTypeCoercion. For example, env.addTypeCoercion('integer', function(x) { return parseInt(x, 10); }) then validate with {useCoerce: true}.

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