React Form Validation

React Form Validation

Before submitting data to the server, it is important to ensure all required form controls are filled out, in the correct format. This is called client-side form validation, and helps ensure data submitted matches the requirements set forth in the various form controls.

This article teaches basic React form validation using controlled state inside of components. We use classes and plan to have a follow up article on doing the same thing with React Hooks.

I think you can all catch up from below code,

import React, { Component } from 'react';
import { render } from 'react-dom';
import './style.css';

class App extends Component {
  render() {
    return (
      <Register />
    );
  }
}

const validEmailRegex = RegExp(/^(([^<>()\[\]\.,;:\s@\"]+(\.[^<>()\[\]\.,;:\s@\"]+)*)|(\".+\"))@(([^<>()[\]\.,;:\s@\"]+\.)+[^<>()[\]\.,;:\s@\"]{2,})$/i);


const validateForm = (errors) => {
  let valid = true;
  Object.values(errors).forEach(
    (val) => val.length > 0 && (valid = false)
  );
  return valid;
}

class Register extends Component {
  constructor(props) {
    super(props);

    this.state = {
      fullName: null,
      email: null,
      password: null,
      errors: {
        fullName: '',
        email: '',
        password: '',
      }
    };

  }

  handleChange = (event) => {
    event.preventDefault();
    const { name, value } = event.target;
    let errors = this.state.errors;

    switch (name) {
      case 'fullName': 
        errors.fullName = 
          value.length < 5
            ? 'Full Name must be 5 characters long!'
            : '';
        break;
      case 'email': 
        errors.email = 
          validEmailRegex.test(value)
            ? ''
            : 'Email is not valid!';
        break;
      case 'password': 
        errors.password = 
          value.length < 8
            ? 'Password must be 8 characters long!'
            : '';
        break;
      default:
        break;
    }

    this.setState({errors, [name]: value});
  }

  handleSubmit = (event) => {
    event.preventDefault();
    if(validateForm(this.state.errors)) {
      console.info('Valid Form')
    }else{
      console.error('Invalid Form')
    }
  }

  render() {
    const {errors} = this.state;
    return (
      <div className='wrapper'>
        <div className='form-wrapper'>
          <h2>Create Account</h2>
          <form onSubmit={this.handleSubmit} noValidate>
            <div className='fullName'>
              <label htmlFor="fullName">Full Name</label>
              <input type='text' name='fullName' onChange={this.handleChange} noValidate />
              {errors.fullName.length > 0 && 
                <span className='error'>{errors.fullName}</span>}
            </div>
            <div className='email'>
              <label htmlFor="email">Email</label>
              <input type='email' name='email' onChange={this.handleChange} noValidate />
              {errors.email.length > 0 && 
                <span className='error'>{errors.email}</span>}
            </div>
            <div className='password'>
              <label htmlFor="password">Password</label>
              <input type='password' name='password' onChange={this.handleChange} noValidate />
              {errors.password.length > 0 && 
                <span className='error'>{errors.password}</span>}
            </div>
            <div className='info'>
              <small>Password must be eight characters in length.</small>
            </div>
            <div className='submit'>
              <button>Create</button>
            </div>
          </form>
        </div>
      </div>
    );
  }
}

render(<App />, document.getElementById('root'));

Conclusion

We are just scraping the surface here, there is so much more we can do when implementing custom validation. There are many solutions out there that make it easy to do do validation, but an exercise like this one although very basic helps us to understand how to get started rolling our own validation rather than relying on a third part to do so.