Question 1

How does JSEN compare to Ajv in terms of speed?

Accepted Answer

JSEN often outperforms Ajv in benchmarks due to its dynamic code generation for V8 optimization, but Ajv supports newer JSON Schema drafts and has a larger ecosystem. For pure Draft 4 validation, JSEN is faster, but Ajv is more feature-rich for modern use.

Question 2

How to add custom error messages in JSEN?

Accepted Answer

Use the invalidMessage and requiredMessage keywords in your schema for specific properties, or define messages globally in a messages object. For example, set invalidMessage: 'Invalid username' on a property to override default errors for validation failures.

Question 3

Does JSEN support JSON Schema Draft 7?

Accepted Answer

No, JSEN only supports Draft 4 of the JSON Schema specification. If you need Draft 7 features like if-then-else or updated format validators, you'll need to use a different validator like Ajv or tv4.

Question 4

Can JSEN fetch remote schemas automatically?

Accepted Answer

No, JSEN does not automatically fetch remote schemas. You must manually download them and pass them via the schemas option in the validator builder, such as providing 'http://example.com/schema.json' as a key with the schema object.

Question 5

How to use JSEN in a browser environment?

Accepted Answer

Include the dist/jsen.min.js script from CDN or Bower, which exposes jsen globally. Then, call jsen(schema) to create validators. It works with globals, AMD, or CommonJS, but ensure CSP allows dynamic code execution.

Question 6

What are the security risks with JSEN's code generation?

Accepted Answer

Since JSEN generates and executes code dynamically, it could be vulnerable to injection attacks if schemas are from untrusted sources. Always validate schemas beforehand and avoid using in sandboxed environments that restrict eval-like behavior.

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