How to Create Form Validation using ReactJS

by vsasikalabe Updated: Jan 24, 2023

Form validation is a process of checking the correctness of the information entered by the user. The form would send an alert message to the user if they entered some invalid information (or something different than the typical input; else, it would proceed with the registration or signup process.

We can validate the form in reactjs by using the “handleChange” function. Whenever users enter some input element, the “onChange” event handler function will create an event object and pass it to the handleChange function.

handleChange(): It is used to handle input change. In handleChange function, the update state function is called, which updates the state of your component as per the value from the event.
onChange: As the name suggests, this event occurs when a change is made to the input value. So, the function passed in the onChange prop will be called whenever some input text is entered.

Let us understand this by taking a real-life example. Suppose we have a form with five inputs:

Roll Number
Name
Phone Number
Marks
Email Id

Now, we can create a function to check the maximum length for the name, phone number, or the correct email format. Also, we can create a function that will be called if any invalid information is found and will throw an error message.

Here is an example of how to create form validation using ReactJS;

Preview of the output that you will get on running this code from your IDE

Code:

In this solution we use the React library.

How to validate my form elements using reactjs?

JavaScriptLines of Code : 54License : CC BY-SA 4.0

import React, { useState } from 'react';
import PropTypes from 'prop-types';

function MyComponent() {
  const initialState = {
    userName: '',
    password: '',
    error: ''
  }

  const [values, setValues] = useState(initialState);

  const handleInputChange = event => {
    const { name, value } = event.target;

    setValues({ ...values, [name]: value.trim() });
  };

  const handleSubmit = event => {
    event.preventDefault();

    if (values.userName.length === 0 || values.password.length === 0) {
      setValues({ ...values, error: "Please fill this field" });
    }
    else {
      setValues({ ...values, error: "" });
    }

    // Handle form submission
    console.log("formData", values);
  };

  return (
    //call handleInputChange on state change event
    //call handleSubmit on onSubmit event
    //display the div containing the error and apply the error class
    <form onSubmit={handleSubmit}>
      {values.error && <div>{values.error}</div>}

      <input type='text' name='userName' placeholder="User Name" value={values.userName || ''} onChange={handleInputChange} />
      <input type='password' name='password' placeholder="Password" value={values.password || ''} onChange={handleInputChange} />
      <button type="submit">Submit</button>
    </form>
  )
}

MyComponent.propTypes = {
  userName: PropTypes.string.isRequired,
  password: PropTypes.string.isRequired,
  error: PropTypes.string.isRequired
};

export default MyComponent;

Instructions

Follow the steps carefully to get the output easily.

Install the Node.js and React on your IDE(preferable Visual Studio Code).
Create React Application using npx create-react-app foldername.
cd foldername.
npm i prop-types.
Open the folder in IDE.
Copy the code using "copy" button above and paste it in App.js file(remove the earlier code from App.js).
Open the terminal from IDE.
npm start to run the file.

I hope you found this useful. I have added the link to dependent libraries, version information in the following sections.

I found this code snippet by searching for 'Create Form Validation using Reactjs' in kandi. You can try any such use case!

Environment Tested

I tested this solution in the following versions. Be mindful of changes when working with other versions.

The solution is created in VS Code 1.73.1 version.
The solution is tested on Nodejs 16.14.2 version.
react 18.2.0 version.
prop-types: 15.8.1 version

Using this solution, we are able to create Form Validation using Reactjs with simple steps. This process also facilities an easy way to use, hassle-free method to create a hands-on working version of code which would help us to create Form Validation using Reactjs.