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How to Validate a Form With Next.js

Have you ever tried to submit a form, only for the web page to give you an error message telling you that one or more fields are invalid? If so, then you have experienced form validation.

Validation is often important to get clean and usable data. From the email address to the date, if it needs to be accurate, you need to check it carefully.

What is Form Validation?

Form validation is the process of ensuring that the data entered into the form by the user is correct and complete. You can do this on the client side, using built-in HTML features such as required attributes. You can also validate on the client using JavaScript, and there is an external Next.js library to help ease the process.

There are several reasons why form validation is so important. First, it helps ensure that the data entered into the form is complete and correct. This is important because it helps prevent errors when your application sends data to a server or database.

Second, form validation can help improve form usability by providing feedback when users enter invalid data. This can help avoid frustration and confusion on the part of the user.

Finally, form validation can help improve form security by ensuring the form only submits valid data.

How to Validate a Form in Next.js

There are two ways to validate forms in Next.js: using the built-in methods or using an external library.

Using the Default Method

HTML provides several methods for validating forms, the most common of which are: needed attribute. This ensures that the field cannot be empty. You can use this method from your Next.js application, simply by entering the attribute in the input tag you create. HTML also provides pattern attribute. You can use this in conjunction with regular expressions for more complex validation.

This example includes a form with two fields: name and email. The name field is required, and the email field must match the regular expression.

import React from 'react'

class MyForm extends React.Component {
render() {
return (
<form >
<label>
Name:
<input type="text" name="name" required />
</label>
<label>
Email:
<input type="email" name="email"
pattern="[a-z0-9._%+-][email protected][a-z0-9.-]+.[a-z]{2,}$" />
</label>
<input type="submit" value="Submit" />
</form>
)
}
}

export default MyForm

This code imports the React library, then creates a class called MyForm and renders the form elements. Inside the form element, there are two label elements.

The first label element contains the required text input fields. The second label element contains an email input field with a regular expression in its pattern attribute.

Finally, you have a submit button. When a user submits a form, the required attribute ensures that they fill in the name field. The email field pattern attribute ensures the email is in the specified format. If any of these conditions fail, the form will not be submitted.

There are some drawbacks to using the built-in method. First, it can be difficult to keep track of all the different validation rules you’ve set up. Second, if you have a lot of fields, it can be tedious to add the required attributes to each one. Finally, the built-in method provides only basic validation. If you want to do more complex validation, you need to use an external library.

Using External Libraries

In addition to the built-in methods, there are also many external libraries that you can use to validate forms. Some popular libraries include Formik, react-hook-form, and Yup.

To use an external library, you must first install it. For example, to install Formik, run the following command:

npm install formik

Once you have the library installed, you can import it into your component and use it to validate your form:

import React from 'react'
import { Formik, Form, Field } from 'formik'

const MyForm = () => (
<Formik
initialValues={{ name: '', email: '' }}
validate={values => {
const errors = {}
if (!values.name) {
errors.name = 'Required'
}
if (!values.email) {
errors.email = 'Required'
} else if (
!/^[A-Z0-9._%+-][email protected][A-Z0-9.-]+.[A-Z]{2,}$/i.test(values.email)
) {
errors.email = 'Invalid email address'
}
return errors
}}
onSubmit={(values, { setSubmitting }) => {
setTimeout(() => {
alert(JSON.stringify(values, null, 2))
setSubmitting(false)
}, 400)
}}
>
{({ isSubmitting }) => (
<Form>
<Field type="text" name="name" />
<Field type="email" name="email" />
<button type="submit" disabled={isSubmitting}>
Submit
</button>
</Form>
)}
</Formik>
)

export default MyForm

Here, you first import format, Shapingand Field components of the Formik library. Next, create a component named MyForm. This component renders a form that has two fields: name and email.

The initialValues ​​prop sets the initial value of the form field. In this case, the name and email fields are empty strings.

The validation prop sets the validation rules for the form fields. In this case, the name field is required, and the email field must match the regular expression.

The onSubmit prop sets the function that React will call when the user submits the form. In this case, the function is an alert that will display the value of the form field.

The isSubmitting prop determines whether the form is being submitted. In this case, you set it to false.

Finally, render the form using the Form component from Formik.

Benefits of Using External Libraries in Next.js

There are several benefits to using an external library like Formik to validate forms in Next.js. One benefit is that it is much easier to display error messages to users. For example, if a required field is not filled in, Formik will automatically display an error message including a suggested fix.

Another benefit is that Formik can handle more complex validation rules. For example, you can use Formik to validate that two fields are the same (such as a password field and a confirm password).

Finally, Formik makes it easy to send form data to the server. For example, you can use Formik to submit form data to an API.

Increase User Engagement Using Forms

You can use forms to increase user engagement. By providing feedback when users enter invalid data, you can help avoid frustration and confusion.

Using external libraries, you can add features such as autocomplete and conditional fields. This can help make your forms more user-friendly. When used properly, forms can be a powerful tool to help you increase user engagement and gather the data you need.

Apart from validation, Next.js has many features that you can use to increase user engagement.

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