What are some examples of using Joi for validation?

What are some examples of using Joi for validation?

Joi is a powerful schema description language and data validator for JavaScript. Here are a few examples:

1. String Validation: You can validate a string to ensure it meets certain criteria, like being an email.

   const Joi = require('joi');
   const schema = Joi.string().email();
   const result = schema.validate('[email protected]');
   

2. Number Validation: You can check if a number is within a specific range.

   const schema = Joi.number().min(1).max(10);
   const result = schema.validate(5);
   

3. Object Validation: You can validate an object with multiple fields.

   const schema = Joi.object({
       name: Joi.string().required(),
       age: Joi.number().integer().min(0)
   });
   const result = schema.validate({ name: 'John', age: 30 });
   

Would you like to see more examples or specific use cases?

Can you show me how to validate an array of objects?

Certainly! To validate an array of objects, you can use Joi's array() method along with items(). Here's an example:

const Joi = require('joi');

const schema = Joi.array().items(Joi.object({
    name: Joi.string().required(),
    age: Joi.number().integer().min(0)
}));

const result = schema.validate([
    { name: 'Alice', age: 25 },
    { name: 'Bob', age: 30 }
]);

This will validate that each item in the array is an object with a name and age. If any item fails the validation, it will return an error.

What happens if the validation fails?

If the validation fails, Joi will return an error object that contains details about what went wrong. For example:

const result = schema.validate([{ name: 'Alice' }]); // Missing age
if (result.error) {
    console.log(result.error.details);
}

The details array will provide information about the specific validation errors, such as which field failed and why.