I'm trying to create a reusable function which you can pass in a joi schema and run validation against req.body. I want to validate my variable schema to ensure that it's a valid joi schema.

Is there a way to do this?

function validatePayload(schema) {
  return (req, res, next) => {
    const valid = joi.validate(req.body, schema)
    if (valid.error) {
      return handleErr(res, HttpStatus.BAD_REQUEST, valid.error.details[0].message)
    }

    return next()
  }
}

I'm trying to create a reusable function which you can pass in a joi schema and run validation against req.body. I want to validate my variable schema to ensure that it's a valid joi schema.

Is there a way to do this?

function validatePayload(schema) {
  return (req, res, next) => {
    const valid = joi.validate(req.body, schema)
    if (valid.error) {
      return handleErr(res, HttpStatus.BAD_REQUEST, valid.error.details[0].message)
    }

    return next()
  }
}

• javascript
• node.js
• joi

2 Answers 2

It appears that Joi internally validates a schema by checking if Joi constructor is found in the schema prototype chain, therefore, you probably can use the same validation:

const mySchema = Joi.object().keys({
  username: Joi.string(),
  password: Joi.string()
});

const isValidSchema = mySchema instanceof Joi.constructor;

console.log(isValidSchema);

<script src="https://cdn.jsdelivr/npm/[email protected]/dist/joi-browser.min.js"></script>

There is now a dedicated method to check if supplied object is a schema

const Joi = require('@hapi/joi')

const schema = Joi.any();
Joi.isSchema(schema); // true

const notSchema = {}
Joi.isSchema(notSchema); // false

https://hapi.dev/module/joi/api/?v=17.1.1#isschemaschema-options