How to Conditionally Validate Array Fields with Yup | Codementor

How to Conditionally Validate Array Fields with Yup

Yup is a powerful JavaScript library that allows you to create schema validations for your data. It provides a simple and intuitive way to define validation rules and apply them to your forms or data objects. One of the key features of Yup is the ability to conditionally validate fields based on certain criteria. In this article, we will explore how to conditionally validate array fields with Yup.

Yup provides a method called `when` that allows you to define conditional validations. This method takes two arguments: a field name and a callback function. The callback function receives the current value of the field and returns a schema object that defines the validation rules for that field.

To conditionally validate array fields, you can use the `when` method in combination with the `test` method. The `test` method allows you to define custom validation rules based on the current value of the field.

Let’s say we have a form with an array field called “items”. We want to validate this field only if another field called “category” has a specific value. Here’s how you can achieve this using Yup:

“`javascript

import * as Yup from ‘yup’;

const schema = Yup.object().shape({

category: Yup.string().required(),

items: Yup.array().when(‘category’, {

is: (value) => value === ‘specificValue’,

then: Yup.array().required(‘Items are required’),

otherwise: Yup.array()

})

});

“`

In the above example, we define a schema object using the `object` method from Yup. We then define two fields: “category” and “items”. The “category” field is required, while the “items” field is conditionally required based on the value of “category”.

The `when` method is used to conditionally validate the “items” field. It takes the name of the field to be validated and a callback function. The callback function receives the current value of the field and returns a schema object that defines the validation rules for that field.

In the callback function, we use the `is` property to check if the value of “category” is equal to ‘specificValue’. If it is, we define the validation rule for the “items” field using the `then` property. In this case, we require the “items” field and display an error message if it is not provided.

If the value of “category” is not equal to ‘specificValue’, we define the validation rule for the “items” field using the `otherwise` property. In this case, we do not require the “items” field.

By using the `when` method in combination with the `test` method, you can conditionally validate array fields in your forms or data objects. This allows you to create more flexible and dynamic validation rules based on specific criteria.

In conclusion, Yup provides a powerful and flexible way to conditionally validate array fields. By using the `when` method in combination with the `test` method, you can define custom validation rules based on specific criteria. This allows you to create more robust and dynamic validations for your forms or data objects.

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