const Joi = require("joi");
const schema = Joi.object({
name: Joi.string(),
email: Joi.string().email().required(),
}).external((value) => {
if (value.name === "John") value.name = "Jonathan";
return value;
});
const data = {
name: "John", email: 'jane@example.com'
};
await schema.validateAsync(data);
Created from: https://npm.runkit.com/joi