validate.js

var Joi = require('joi');

var schema = Joi.object().keys({
  id: Joi.any(),
  type: Joi.string(),
  respondsTo: Joi.func().required(),
  script: Joi.string().required(),
  connections: Joi.array().required(),
})

var toValidate = {
  id: 1,
  type: 'RootScript',
  respondsTo: () => {},
  script: 'wat',
  connections: [2],
}

new Promise((resolve, reject) => {
  Joi.validate(toValidate, schema, function (err, value) {
    if (!err) return resolve()
    reject(err.details[0].message)
  })
}).then(() => {
  console.log('Success')
}).catch((error) => {
  console.log(error)
})