How to Use Joi to Transform and Validate Your Data Values

Joi is a robust library that empowers developers to validate and transform their data values in a convenient way. It is widely used by Node.js developers to streamline their development workflow and ensure data consistency. Joi makes it easy to define schema for your data and apply validation and transformation rules on them. In this article, we will explore how to use Joi to transform and validate your data values.

Defining Joi schema

Joi allows developers to define the structure of their data in a schema. The schema can describe the shape of the data and the rules that need to be applied to it. Let’s consider an example of defining a schema for an email validation.

“`
const Joi = require(‘joi’);

const emailSchema = Joi.object({
email: Joi.string().email().required(),
});
“`

In the above code, we used the `Joi.object()` method to define the schema object, which has a property `email` that should be a `Joi.string()` and should be in email format using `Joi.email()`. We also set it as required using the `Joi.required()` method.

Using Joi for validation

We can use the emailSchema defined above to validate email data. Here’s an example of how to use it:

“`
const emailInput = {
email: ‘[email protected]’
};

const { error, value } = emailSchema.validate(emailInput);

if (error) {
console.log(error.message);
} else {
console.log(value.email);
}
“`

In the above code, we defined an email input object and passed it through the email schema. We then checked if the `error` object is null, meaning the validation was successful, and we logged the email value from the `value` object.

Using Joi for transformation

Joi also lets us transform data values based on rules defined in the schema. Let’s take an example where we want to convert a string to uppercase.

“`
const Joi = require(‘joi’);

const strSchema = Joi.string().uppercase();
const transformedStr = strSchema.validate(‘hello world’).value;
console.log(transformedStr);
“`

In the above code, we defined a `strSchema` object that will convert a string value to uppercase using the `Joi.uppercase()` method. We then applied this schema to a string value and logged the transformed value.

Conclusion

Joi is a versatile library that lets developers validate and transform their data values with ease. By using Joi, we can ensure the consistency and accuracy of our data, preventing errors and saving us time in the development process. With Joi, we can define schemas for our data, specify validation rules, and apply transformations using simple and intuitive methods. By mastering Joi, developers can improve their development skills and produce higher quality projects.