Form not submitting properly using Reactjs

Form not submitting properly using Reactjs - javascript

I am working with Reacjs/nextjs,Right now i am trying to submit "login form" i am getting alert but page is also reloading,I just want page should not reload,Where i am wrong ? Here is my current code in "index.tsx"
import React from 'react';
import axios from 'axios';
const LoginForm = () => {
const [formValue, setformValue] = React.useState({
email: '',
password: ''
});
const handleSubmit = (event) => {
alert("its workinggg");
// we will fill this in the coming paragraph
}
const handleChange = (event) => {
setformValue({
...formValue,
[event.target.name]: event.target.value
});
}
return (
<form onSubmit={handleSubmit}>
<p>Login Form</p>
<input
type="email"
name="email"
placeholder="enter an email"
value={formValue.email}
onChange={handleChange}
/>
<input
type="password"
name="password"
placeholder="enter a password"
value={formValue.password}
onChange={handleChange}
/>
<button
type="submit"
>
Login
</button>
</form>
)
};
export default LoginForm;

Use preventDefault method to prevent default reload.
It works with all events which have default action.
const LoginForm = () => {
const [formValue, setformValue] = React.useState({
email: '',
password: ''
});
const handleSubmit = (event) => {
event.preventDefault() // <----- HERE
alert("its workinggg");
// we will fill this in the coming paragraph
}
const handleChange = (event) => {
setformValue({
...formValue,
[event.target.name]: event.target.value
});
}
return (
<form onSubmit={handleSubmit}>
<p>Login Form</p>
<input
type="email"
name="email"
placeholder="enter an email"
value={formValue.email}
onChange={handleChange}
/>
<input
type="password"
name="password"
placeholder="enter a password"
value={formValue.password}
onChange={handleChange}
/>
<button
type="submit"
>
Login
</button>
</form>
)
};

Related

how to add validation to a reactjs form

I have developed a registration form and I tried using validation format but it is not working. I don't know how and where to code a function for it and apply it. please help me how to do it. I will attach the code i have done till now.
import React, { useState } from 'react';
import { Button, Form } from 'semantic-ui-react'
import axios from 'axios';
import { useNavigate } from 'react-router';
export default function Create() {
let navigate = useNavigate();
const [Employee_name, setEmployee_name] = useState('');
const [Employee_id, setEmployee_id] = useState('');
const [Employee_address, setEmployee_address] = useState('');
const [Employee_post, setEmployee_post] = useState('');
const postData = () => {
axios.post(`http://localhost:5000/qo`, {
Employee_name,
Employee_id,
Employee_address,
Employee_post
}).then(() => {
navigate('/read')
})
alert('Data Saved')
}
return (
<div>
<Form className="create-form">
<Form.Field required={true}>
<label>Employee Name</label>
<input placeholder='Employee Name' onChange={(e) => setEmployee_name(e.target.value)} required={true}/>
</Form.Field>
<Form.Field required={true}>
<label>Employee ID</label>
<input placeholder='Employee ID' onChange={(e) => setEmployee_id(e.target.value)} required={true}/>
</Form.Field>
<Form.Field required={true}>
<label>Employee Address</label>
<input placeholder='Employee Address' onChange={(e) => setEmployee_address(e.target.value)} required={true}/>
</Form.Field>
<Form.Field required={true}>
<label>Employee Position</label>
<input placeholder='Employee Position' onChange={(e) => setEmployee_post(e.target.value)} required={true}/>
</Form.Field>
<Button onClick={postData} type='submit'>Submit</Button>
</Form>
</div>
)
}

There are good libraries out there, that can help you with form validation before allowing a user to submit the form.
One such library could be formik together with Yup.
This is how I do client side form validation on my forms:
Login schema (made with Yup):
import * as Yup from 'yup';
const loginSchema = Yup.object().shape({
username: Yup.string()
.min(3, 'Minimum 3 chars')
.max(50, 'Max 50 chars')
/* password: Yup.string()
.min(6, 'Minimum 6 chars')
.max(50, 'Max 50 chars')
*/
});
Login component:
export const Login = () => {
const [loading, setLoading] = useState(false);
const formik = useFormik({
initialValues: {
username: ''
},
validationSchema: loginSchema,
onSubmit: async (values, {setStatus, setSubmitting}) => {
setLoading(true);
setStatus(null);
try {
// Call your API function to post to the backend here
// You can access your form values in the "values" parameter
setLoading(false);
} catch (error) {
console.error(error);
setStatus('User not found');
setSubmitting(false);
setLoading(false);
}
}
});
}
return (
<form
onSubmit={formik.handleSubmit}
className={'auth-form-wrapper'}
>
{/* begin::Heading */}
<div className={'auth-form-header'}>
<h1>Log in</h1>
<div className={'auth-error-message-container'}>
formik.status && (
<p className={'error-message'}>{formik.status}</p>
)
}
</div>
</div>
{/* end::Heading */}
{/* begin::Form group content */}
<div className={'auth-form-content'}>
{/* begin::Form group */}
<div className={'dynamic-input-container'}>
<input type='text'
id="username"
value={formik.values.username}
onChange={formik.handleChange}
placeholder='Username'
className={'dynamic-input auth-input ' + clsx(
{'is-invalid': formik.touched.username && formik.errors.username},
{
'is-valid': formik.touched.username && !formik.errors.username
}
)}
autoComplete='off'
/>
{formik.touched.username && formik.errors.username && (
<div className='fv-plugins-message-container'>
<span role='alert'>{formik.errors.username}</span>
</div>
)}
</div>
{/* end::Form group*/}
{/* begin::Action */}
<div className='auth-btn-container'>
<Button variant="contained" size="medium" type={'submit'} disabled={loading}>
{
!loading ? <span>Continue</span>
:
(
<span className={'auth-spinner-container'}>
<ClipLoader
loading={loading}
size={20}
aria-label='Loading Spinner'
/>
</span>
)
}
</Button>
</div>
{/* end::Action */}
</div>
{/* end::Form group content */}
</form>
);
Please note, that in my example I only have a "username" input, but you can obviously add as many fields as you wish.
Documentation:
Formik: https://formik.org/docs/tutorial
Yup: https://www.npmjs.com/package/yup
clxs: https://www.npmjs.com/package/clsx

import React, { useState } from 'react';
import { Button, Form } from 'semantic-ui-react'
import axios from 'axios';
import { useNavigate } from 'react-router';
export default function Create() {
let navigate = useNavigate();
const [Employee_name, setEmployee_name] = useState('');
const [Employee_id, setEmployee_id] = useState('');
const [Employee_address, setEmployee_address] = useState('');
const [Employee_post, setEmployee_post] = useState('');
const postData = e => {
e.preventDefault();
if(Employee_name.length == 0) return false;
if(Employee_id.length == 0) return false;
if(Employee_address.length == 0) return false;
if(Employee_post.length == 0) return false;
axios.post(`http://localhost:5000/qo`, {
Employee_name,
Employee_id,
Employee_address,
Employee_post
}).then(() => {
navigate('/read')
})
alert('Data Saved')
}
return (
<div>
<Form className="create-form" onSubmit={e => postData(e)}>
<Form.Field required={true}>
<label>Employee Name</label>
<input placeholder='Employee Name' onChange={(e) => setEmployee_name(e.target.value)} required={true}/>
</Form.Field>
<Form.Field required={true}>
<label>Employee ID</label>
<input placeholder='Employee ID' onChange={(e) => setEmployee_id(e.target.value)} required={true}/>
</Form.Field>
<Form.Field required={true}>
<label>Employee Address</label>
<input placeholder='Employee Address' onChange={(e) => setEmployee_address(e.target.value)} required={true}/>
</Form.Field>
<Form.Field required={true}>
<label>Employee Position</label>
<input placeholder='Employee Position' onChange={(e) => setEmployee_post(e.target.value)} required={true}/>
</Form.Field>
<Button type='submit'>Submit</Button>
</Form>
</div>
)
}
This is updated code from your snippet. try this and let me know what's the progress.
I really appreciate you.

How to convert Class component to function on react

I have a customer feedback page or rather a contact page. There are a few in there. The page is written in JavaScript, React in the class component. I want to convert it to a functional component.
Below I will throw source code off the page
import React, { Component } from "react";
import { Button, Form, FormGroup, Label, Input, FormText } from "reactstrap";
import axios from "axios";
class Contacts extends Component {
constructor(props) {
super(props);
this.state = {
name: "",
email: "",
subject: ""
};
this.handleChange = this.handleChange.bind(this);
this.handleSubmit = this.handleSubmit.bind(this);
}
handleChange = e => {
this.setState({ [e.target.name]: e.target.value });
//console.log(`${e.target.name}:${e.target.value}`);
};
async handleSubmit(e) {
e.preventDefault();
const { name, email, subject } = this.state;
const form = await axios.post("/api/form", {
name,
email,
subject
});
}
render() {
return (
<Form className="col-xs-12 col-md-6" onSubmit={this.handleSubmit}>
<FormGroup>
<Label for="name">name:</Label>
<Input type="text" name="name" onChange={this.handleChange} />
</FormGroup>
<FormGroup>
<Label for="exampleEmail">Email:</Label>
<Input type="email" name="email" onChange={this.handleChange} />
</FormGroup>
<FormGroup>
<Label for="subject">Subject:</Label>
<Input type="textarea" name="subject" onChange={this.handleChange} />
</FormGroup>
<Button>Submit</Button>
</Form>
);
}
}
export default Contacts;

1- first create a functional component like below:
2- add some hooks for the state:
3- Refactor functions in a new way:
4- At the end add the return section.
Finally you have something like this:
export default function Contacts() {
const [state, setState] = useState({
name: '',
email: '',
subject: '',
});
const handleChange = (e) => {
setState({ [e.target.name]: e.target.value });
//console.log(`${e.target.name}:${e.target.value}`);
};
const handleSubmit = async (e) => {
e.preventDefault();
const { name, email, subject } = state;
const form = await axios.post('/api/form', {
name,
email,
subject,
});
};
return (
<Form className="col-xs-12 col-md-6" onSubmit={handleSubmit}>
<FormGroup>
<Label for="name">name:</Label>
<Input type="text" name="name" onChange={handleChange} />
</FormGroup>
<FormGroup>
<Label for="exampleEmail">Email:</Label>
<Input type="email" name="email" onChange={handleChange} />
</FormGroup>
<FormGroup>
<Label for="subject">Subject:</Label>
<Input type="textarea" name="subject" onChange={handleChange} />
</FormGroup>
<Button>Submit</Button>
</Form>
);
}

const Contacts = (props) => {
const [name, setName] = useState();
const [email, setEmail] = useState();
const [subject, setSubject] = useState();
const handleChange = useCallback((setState, event) => {
setState(event.target.value);
}, []);
const handleSubmit = useCallback(async () => {
const response = await axios.post("/api/form", {
name,
email,
subject
});
console.log(response)
}, [name, email, subject]);
return (
<Form className="col-xs-12 col-md-6" onSubmit={handleSubmit}>
<FormGroup>
<Label for="name">name:</Label>
<Input type="text" name="name" onChange={handleChange.bind(null, setName)} />
</FormGroup>
<FormGroup>
<Label for="exampleEmail">Email:</Label>
<Input type="email" name="email" onChange={handleChange.bind(null, setEmail)} />
</FormGroup>
<FormGroup>
<Label for="subject">Subject:</Label>
<Input type="textarea" name="subject" onChange={handleChange.bind(null, setSubject)} />
</FormGroup>
<Button>Submit</Button>
</Form>
);
}

Resetting React Form values after validation

have that problem with resetting the values of the input fields in the form. and wanted to ask if somebody knows a better and way to do that instead of just making 'useState' for every field...
const handleSubmit = (e) => {
e.preventDefault();
emailjs.sendForm('sample_id', 'someother_id', formRef.current, 'user_is')
.then((result) => {
console.log(result.text);
}, (error) => {
console.log(error.text);
});
setMessage(true);
setEmail("");
setName("");
setSubject("");
setTextarea("");
};
return (
<div className="contact" id="contact">
<div className="left">
<img src="" alt="" />
</div>
<div className="right">
<h2>Kontakt</h2>
<form ref={formRef} onSubmit={handleSubmit}>
<label>Name</label>
<input onChange={(e) => setName(e.target.value)} type="text" placeholder="Name" name="user_name" value={name} />
<label>Email</label>
<input onChange={(e) => setEmail(e.target.value)} type="email" placeholder="Email" name="user_email" value={email} />
<label>Betreff</label>
<input onChange={(e) => setSubject(e.target.value)} type="text" placeholder="Subject" name="user_subject" value={subject} />
<label>Nachricht</label>
<textarea onChange={(e) => setTextarea(e.target.value)} placeholder="Message" name="message" value={textarea} />
<button type="submit">Send</button>
{message && <span>Thanks we will respond ASAP.</span>}
</form>
</div>
</div>
)
}

You could use a single state for all the form values (kinda like we did before functional components)
// this could be outside your component
const initialState = { email: "", name: "", subject: "", textArea: ""};
// declaring your state
const [formState, setFormState] = React.useState(initialState);
and then
const handleSubmit = (e) => {
e.preventDefault();
emailjs.sendForm('sample_id', 'someother_id', formRef.current, 'user_is')
.then((result) => {
console.log(result.text);
}, (error) => {
console.log(error.text);
});
setMessage(true);
setFormState(initialState)
};
You also would have to rewrite your input handlers. Like that :
<input onChange={(e) => setFormState({...formState, name: e.target.value})} type="text" placeholder="Name" name="user_name" value={name} />

Cannot read property 'value' of null in ReactJS

I've been trying to console.log these 2 inputs, but can't seem to figure it out, can anyone tell me what I've done wrong?
I keep getting the Cannot read property 'value' of null error
function printInputs() {
let username = document.getElementById('user').value
let password = document.getElementById('pass').value
console.log(username);
console.log(password);
}
function App() {
return (
<div className="App">
<h1>Log In</h1>
<h1>{code}</h1>
<form>
<input className='userInput' id='user' type='text' placeholder='username' /><br />
<input className='userInput' id='pass' type='password' placeholder='password' /><br />
<input className='userSubmit' type='submit' value='Log In' onSubmit={printInputs()} />
</form>
</div>
);
}

onSubmit={printInputs()}
You are trying to call printInputs immediately (before the render function has returned anything so before the inputs are in the page).
You need to pass a function to onSubmit:
onSubmit={printInputs}
That said, this is not the approach to take for getting data from forms in React. See the Forms section of the React guide for the right approach.

The way to write forms in react. Working example demo
function App() {
const [state, setState] = React.useState({ username: "", password: "" });
const handleSubmit = e => {
e.preventDefault();
console.log(state);
};
const handleChange = e => {
setState({
...state,
[e.target.name]: e.target.value
});
};
return (
<div className="App">
<h1>Log In</h1>
<form onSubmit={handleSubmit}>
<input
className="userInput"
name="username"
type="text"
placeholder="username"
onChange={handleChange}
/>
<br />
<input
className="userInput"
name="password"
type="password"
placeholder="password"
onChange={handleChange}
/>
<br />
<input className="userSubmit" type="submit" value="Log In" />
</form>
</div>
);
}

in the first never use real dom to manipulate the dom in
React ,use a state to get de value and the onSumbit is used in Form tag
import React, { useState } from "React";
const App = () => {
const [userName, setUserName] = useState("");
const [password, setPassword] = useState("");
const printInputs = () => {
console.log(userName);
console.log(password);
};
return (
<div className="App">
<h1>Log In</h1>
<form onSubmit={printInputs}>
<input
className="userInput"
id="user"
type="text"
placeholder="username"
onChange={event => setUserName(event.target.value)}
/>
<br />
<input
className="userInput"
id="pass"
type="password"
placeholder="password"
onChange={event => setPassword(event.target.value)}
/>
<br />
<input
className="userSubmit"
type="submit"
value="Log In"/>
</form>
</div>
);
};
export default App;

How do I add validation to the form in my React component?

My Contact page form is as follows,
<form name="contactform" onSubmit={this.contactSubmit.bind(this)}>
<div className="col-md-6">
<fieldset>
<input ref="name" type="text" size="30" placeholder="Name"/>
<br/>
<input refs="email" type="text" size="30" placeholder="Email"/>
<br/>
<input refs="phone" type="text" size="30" placeholder="Phone"/>
<br/>
<input refs="address" type="text" size="30" placeholder="Address"/>
<br/>
</fieldset>
</div>
<div className="col-md-6">
<fieldset>
<textarea refs="message" cols="40" rows="20"
className="comments" placeholder="Message"/>
</fieldset>
</div>
<div className="col-md-12">
<fieldset>
<button className="btn btn-lg pro" id="submit"
value="Submit">Send Message</button>
</fieldset>
</div>
</form>
Need to add validation for all fields. Can anyone help me to add validation in this react form?

You should avoid using refs, you can do it with onChange function.
On every change, update the state for the changed field.
Then you can easily check if that field is empty or whatever else you want.
You could do something as follows :
class Test extends React.Component {
constructor(props) {
super(props);
this.state = {
fields: {},
errors: {},
};
}
handleValidation() {
let fields = this.state.fields;
let errors = {};
let formIsValid = true;
//Name
if (!fields["name"]) {
formIsValid = false;
errors["name"] = "Cannot be empty";
}
if (typeof fields["name"] !== "undefined") {
if (!fields["name"].match(/^[a-zA-Z]+$/)) {
formIsValid = false;
errors["name"] = "Only letters";
}
}
//Email
if (!fields["email"]) {
formIsValid = false;
errors["email"] = "Cannot be empty";
}
if (typeof fields["email"] !== "undefined") {
let lastAtPos = fields["email"].lastIndexOf("#");
let lastDotPos = fields["email"].lastIndexOf(".");
if (
!(
lastAtPos < lastDotPos &&
lastAtPos > 0 &&
fields["email"].indexOf("##") == -1 &&
lastDotPos > 2 &&
fields["email"].length - lastDotPos > 2
)
) {
formIsValid = false;
errors["email"] = "Email is not valid";
}
}
this.setState({ errors: errors });
return formIsValid;
}
contactSubmit(e) {
e.preventDefault();
if (this.handleValidation()) {
alert("Form submitted");
} else {
alert("Form has errors.");
}
}
handleChange(field, e) {
let fields = this.state.fields;
fields[field] = e.target.value;
this.setState({ fields });
}
render() {
return (
<div>
<form
name="contactform"
className="contactform"
onSubmit={this.contactSubmit.bind(this)}
>
<div className="col-md-6">
<fieldset>
<input
ref="name"
type="text"
size="30"
placeholder="Name"
onChange={this.handleChange.bind(this, "name")}
value={this.state.fields["name"]}
/>
<span style={{ color: "red" }}>{this.state.errors["name"]}</span>
<br />
<input
refs="email"
type="text"
size="30"
placeholder="Email"
onChange={this.handleChange.bind(this, "email")}
value={this.state.fields["email"]}
/>
<span style={{ color: "red" }}>{this.state.errors["email"]}</span>
<br />
<input
refs="phone"
type="text"
size="30"
placeholder="Phone"
onChange={this.handleChange.bind(this, "phone")}
value={this.state.fields["phone"]}
/>
<br />
<input
refs="address"
type="text"
size="30"
placeholder="Address"
onChange={this.handleChange.bind(this, "address")}
value={this.state.fields["address"]}
/>
<br />
</fieldset>
</div>
</form>
</div>
);
}
}
React.render(<Test />, document.getElementById("container"));
In this example I did the validation only for email and name, but you have an idea how to do it. For the rest you can do it self.
There is maybe a better way, but you will get the idea.
Here is fiddle.

Try this, example,
the required property in the below input tag will ensure that the name field shouldn't be submitted empty.
<input type="text" placeholder="Your Name" required />

I've taken your code and adapted it with library react-form-with-constraints: https://codepen.io/tkrotoff/pen/LLraZp
const {
FormWithConstraints,
FieldFeedbacks,
FieldFeedback
} = ReactFormWithConstraints;
class Form extends React.Component {
handleChange = e => {
this.form.validateFields(e.target);
}
contactSubmit = e => {
e.preventDefault();
this.form.validateFields();
if (!this.form.isValid()) {
console.log('form is invalid: do not submit');
} else {
console.log('form is valid: submit');
}
}
render() {
return (
<FormWithConstraints
ref={form => this.form = form}
onSubmit={this.contactSubmit}
noValidate>
<div className="col-md-6">
<input name="name" size="30" placeholder="Name"
required onChange={this.handleChange}
className="form-control" />
<FieldFeedbacks for="name">
<FieldFeedback when="*" />
</FieldFeedbacks>
<input type="email" name="email" size="30" placeholder="Email"
required onChange={this.handleChange}
className="form-control" />
<FieldFeedbacks for="email">
<FieldFeedback when="*" />
</FieldFeedbacks>
<input name="phone" size="30" placeholder="Phone"
required onChange={this.handleChange}
className="form-control" />
<FieldFeedbacks for="phone">
<FieldFeedback when="*" />
</FieldFeedbacks>
<input name="address" size="30" placeholder="Address"
required onChange={this.handleChange}
className="form-control" />
<FieldFeedbacks for="address">
<FieldFeedback when="*" />
</FieldFeedbacks>
</div>
<div className="col-md-6">
<textarea name="comments" cols="40" rows="20" placeholder="Message"
required minLength={5} maxLength={50}
onChange={this.handleChange}
className="form-control" />
<FieldFeedbacks for="comments">
<FieldFeedback when="*" />
</FieldFeedbacks>
</div>
<div className="col-md-12">
<button className="btn btn-lg btn-primary">Send Message</button>
</div>
</FormWithConstraints>
);
}
}
Screenshot:
This is a quick hack. For a proper demo, check https://github.com/tkrotoff/react-form-with-constraints#examples

import React from 'react';
import {sendFormData} from '../services/';
class Signup extends React.Component{
constructor(props){
super(props);
this.state = {
isDisabled:true
}
this.submitForm = this.submitForm.bind(this);
}
validateEmail(email){
const pattern = /[a-zA-Z0-9]+[\.]?([a-zA-Z0-9]+)?[\#][a-z]{3,9}[\.][a-z]{2,5}/g;
const result = pattern.test(email);
if(result===true){
this.setState({
emailError:false,
email:email
})
} else{
this.setState({
emailError:true
})
}
}
handleChange(e){
const target = e.target;
const value = target.type === 'checkbox' ? target.checked : target.value;
const name = target.name;
this.setState({
[name]: value
});
if(e.target.name==='firstname'){
if(e.target.value==='' || e.target.value===null ){
this.setState({
firstnameError:true
})
} else {
this.setState({
firstnameError:false,
firstName:e.target.value
})
}
}
if(e.target.name==='lastname'){
if(e.target.value==='' || e.target.value===null){
this.setState({
lastnameError:true
})
} else {
this.setState({
lastnameError:false,
lastName:e.target.value
})
}
}
if(e.target.name==='email'){
this.validateEmail(e.target.value);
}
if(e.target.name==='password'){
if(e.target.value==='' || e.target.value===null){
this.setState({
passwordError:true
})
} else {
this.setState({
passwordError:false,
password:e.target.value
})
}
}
if(this.state.firstnameError===false && this.state.lastnameError===false &&
this.state.emailError===false && this.state.passwordError===false){
this.setState({
isDisabled:false
})
}
}
submitForm(e){
e.preventDefault();
const data = {
firstName: this.state.firstName,
lastName: this.state.lastName,
email: this.state.email,
password: this.state.password
}
sendFormData(data).then(res=>{
if(res.status===200){
alert(res.data);
this.props.history.push('/');
}else{
}
});
}
render(){
return(
<div className="container">
<div className="card card-login mx-auto mt-5">
<div className="card-header">Register here</div>
<div className="card-body">
<form id="signup-form">
<div className="form-group">
<div className="form-label-group">
<input type="text" id="firstname" name="firstname" className="form-control" placeholder="Enter firstname" onChange={(e)=>{this.handleChange(e)}} />
<label htmlFor="firstname">firstname</label>
{this.state.firstnameError ? <span style={{color: "red"}}>Please Enter some value</span> : ''}
</div>
</div>
<div className="form-group">
<div className="form-label-group">
<input type="text" id="lastname" name="lastname" className="form-control" placeholder="Enter lastname" onChange={(e)=>{this.handleChange(e)}} />
<label htmlFor="lastname">lastname</label>
{this.state.lastnameError ? <span style={{color: "red"}}>Please Enter some value</span> : ''}
</div>
</div>
<div className="form-group">
<div className="form-label-group">
<input type="email" id="email" name="email" className="form-control" placeholder="Enter your email" onChange={(e)=>{this.handleChange(e)}} />
<label htmlFor="email">email</label>
{this.state.emailError ? <span style={{color: "red"}}>Please Enter valid email address</span> : ''}
</div>
</div>
<div className="form-group">
<div className="form-label-group">
<input type="password" id="password" name="password" className="form-control" placeholder="Password" onChange={(e)=>{this.handleChange(e)}} />
<label htmlFor="password">Password</label>
{this.state.passwordError ? <span style={{color: "red"}}>Please enter some value</span> : ''}
</div>
</div>
<button className="btn btn-primary btn-block" disabled={this.state.isDisabled} onClick={this.submitForm}>Signup</button>
</form>
</div>
</div>
</div>
);
}
}
export default Signup;

With React Hook, form is made super easy (React Hook Form: https://github.com/bluebill1049/react-hook-form)
i have reused your html markup.
import React from "react";
import useForm from 'react-hook-form';
function Test() {
const { useForm, register } = useForm();
const contactSubmit = data => {
console.log(data);
};
return (
<form name="contactform" onSubmit={contactSubmit}>
<div className="col-md-6">
<fieldset>
<input name="name" type="text" size="30" placeholder="Name" ref={register} />
<br />
<input name="email" type="text" size="30" placeholder="Email" ref={register} />
<br />
<input name="phone" type="text" size="30" placeholder="Phone" ref={register} />
<br />
<input name="address" type="text" size="30" placeholder="Address" ref={register} />
<br />
</fieldset>
</div>
<div className="col-md-6">
<fieldset>
<textarea name="message" cols="40" rows="20" className="comments" placeholder="Message" ref={register} />
</fieldset>
</div>
<div className="col-md-12">
<fieldset>
<button className="btn btn-lg pro" id="submit" value="Submit">
Send Message
</button>
</fieldset>
</div>
</form>
);
}

Assuming you know about react useState Hook, If your form is simple, you can use state variables to hold the value of each input field. Then add onChange handler function on each input field which will update state variables. At the end, you can check the values stored in state variables to ensure that all the input fields had some value. Here is a simple example.
import { useState } from "react";
export default function App() {
const [name, setName] = useState("");
const [email, setEmail] = useState("");
const onChangeHandler = (fieldName, value)=>{
if(fieldName === "name"){
setName(value);
}
else if(fieldName==="email"){
setEmail(value);
}
}
const onSubmitHandler = (e)=>{
e.preventDefault();
if(name.trim()==="" || email.trim() ==""){
alert("required both field");
}
else{
alert(name+" " +email);
setName("");
setEmail("");
}
}
return (
<div className="App">
<form onSubmit={(e)=>{onSubmitHandler(e)}}>
<input type="text" value={name} onChange={(e)=>{ onChangeHandler("name",e.target.value)}} /> <br/>
<input type="email" value={email} onChange={(e)=>{ onChangeHandler("email",e.target.value)}} /> <br/>
<input type="submit" value="Submit" />
</form>
</div>
);
}
However, if you are having a complex form, it's hard to keep each value in state variables and then use validation on each field. For complex forms, it is recommended to use Formik that will do everything for you and you can use Yup validation package which is also supported by Formik that will allow you to add more than just simple validation.

2022
React suggests 3 approaches to handle forms:
Controlled components - In HTML, form elements such as <input>, <textarea>, and <select> typically maintain their own state and update it based on user input. In React, mutable state is typically kept in the state property of components, and only updated with setState(). We can combine the two by making the React state be the “single source of truth”. Then the React component that renders a form also controls what happens in that form on subsequent user input. An input form element whose value is controlled by React in this way is called a “controlled component”.
Uncontrolled components - It can sometimes be tedious to use controlled components, because you need to write an event handler for every way your data can change and pipe all of the input state through a React component. This can become particularly annoying when you are converting a preexisting codebase to React, or integrating a React application with a non-React library. In these situations, you might want to check out uncontrolled components, an alternative technique for implementing input forms.
Fully-Fledged Solutions - If you’re looking for a complete solution including validation, keeping track of the visited fields, and handling form submission, Formik is one of the popular choices. However, it is built on the same principles of controlled components and managing state — so don’t neglect to learn them.
All approaches are valid to react hooks too.
First consider which component better suit your needs, and use its appropriate validation solution.

We have plenty of options to validate the react js forms. Maybe the npm packages have some own limitations. Based up on your needs you can choose the right validator packages. I would like to recommend some, those are listed below.
react-form-input-validation
redux-form
If anybody knows a better solution than this, please put it on the comment section for other people references.

Cleaner way is to use joi-browser package. In the state you should have errors object that includes all the errors in the form. Initially it shoud be set to an empty object.
Create schema;
import Joi from "joi-browser";
schema = {
username: Joi.string()
.required()
.label("Username")
.email(),
password: Joi.string()
.required()
.label("Password")
.min(8)
.regex(/^(?=.*\d)(?=.*[a-z])(?=.*[A-Z])(?=.*[^a-zA-Z0-9]).{8,1024}$/) //special/number/capital
};
Then validate the form with the schema:
validate = () => {
const options = { abortEarly: false };
const result = Joi.validate(this.state.data, this.schema, options);
console.log(data) // always analyze your data
if (!result.error) return null;
const errors = {};
for (let item of result.error.details) errors[item.path[0]] = item.message; //in details array, there are 2 properties,path and message.path is the name of the input, message is the error message for that input.
return errors;
};
Before submitting the form, check the form:
handleSubmit = e => {
e.preventDefault();
const errors = this.validate(); //will return an object
console.log(errors);
this.setState({ errors: errors || {} }); //in line 9 if we return {}, we dont need {} here
if (errors) return;
//so we dont need to call the server
alert("success");
//if there is no error call the server
this.dosubmit();
};

Might be late to answer - if you don't want to modify your current code a lot and still be able to have similar validation code all over your project, you may try this one too -
https://github.com/vishalvisd/react-validator.

Try powerform-react . It is based upon powerform which is a super portable Javascript form library. Once learnt, it can be used in any framework. It works even with vanilla Javascript.
Checkout this simple form that uses powerform-react
There is also a complex example.

Try this validation plugin in your form where you can add your custom validation rules.
Create a component FormValidation.js
import { useState } from "react";
const FormValidation = ({ validationRules, formInput }) => {
const [errors, setErrors] = useState(null);
const validation = () => {
// define a empty object to store errors.
let allErrors = {};
// Run loop on validation object
Object.keys(validationRules).forEach((name) => {
// name is the name of input field
const rulesArr = validationRules[name];
// Run loop on validation array applied on that input
rulesArr.forEach((rule) => {
// Skip if any error message is already stored in allErrors object
if (!allErrors[name]) {
let result;
// If rule is an array than it is a type of a function with parameter
switch (Array.isArray(rule)) {
case true: {
// take the function name and parameter value from rule array
const [functionName, paramValue] = rule;
// call validation function
result = functionName(formInput, name, paramValue);
break;
}
default:
// call validation function
result = rule(formInput, name);
break;
}
if (result) {
// append error in object
allErrors = { ...allErrors, ...result };
}
}
});
});
return allErrors;
};
const validate = () =>
new Promise((resolve, reject) => {
const errorObj = validation();
if (Object.keys(errorObj).length === 0) {
setErrors({});
resolve("Success");
} else {
setErrors(errorObj);
reject(Error("Some Error Occurred"));
}
});
return { validate, errors, setErrors };
};
export const required = (formInputs, inputName) =>
!formInputs[inputName] && { [inputName]: "This field is required" };
function emailPattern(email) {
return String(email)
.toLowerCase()
.match(
/^(([^<>()[\]\\.,;:\s#"]+(\.[^<>()[\]\\.,;:\s#"]+)*)|(".+"))#((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/
);
}
export const email = (formInputs, inputName) =>
!emailPattern(formInputs[inputName]) && {
[inputName]: "Please enter valid email",
};
export function passwordPattern(formInputs, inputName) {
const value = formInputs[inputName];
let error;
if (value.length < 8) {
error = "Your password must be at least 8 characters";
}
if (value.search(/[a-z]/i) < 0) {
error = "Your password must contain at least one letter.";
}
if (value.search(/[0-9]/) < 0) {
error = "Your password must contain at least one digit.";
}
if (value.search(/[ `!##$%^&*()_+\-=\[\]{};':"\\|,.<>\/?~]/) < 0) {
error = "Your password must contain at least one special character.";
}
return (
error && {
[inputName]: error,
}
);
}
export const maxLength = (formInputs, inputName, paramValue) =>
formInputs[inputName].length > paramValue && {
[inputName]: `Maximum characters are ${paramValue}`,
};
export const minLength = (formInputs, inputName, paramValue) =>
formInputs[inputName].length < paramValue && {
[inputName]: `Minimum characters are ${paramValue}`,
};
export default FormValidation;
I want to implement validations in my Login.js
import React, { useState } from "react";
import { Button, Form } from "react-bootstrap";
import FormValidation, {
required,
email,
passwordPattern,
} from "utils/FormValidation";
const Login = () => {
const [formInput, setFormInput] = useState({
email: "",
password: "",
});
const { validate, errors, setErrors } = FormValidation({
validationRules: {
email: [required, email],
password: [required, passwordPattern],
},
formInput,
});
const handleChange = (e) => {
setFormInput({ ...formInput, [e.target.name]: e.target.value });
};
const handleSubmit = (e) => {
e.preventDefault();
validate().then(() => {
//do whatever you want
console.log(formInput);
// you can set server error manually
setErrors({ email: "Email already exist" });
});
};
return (
<section className="gradient-form" style={{ backgroundColor: "#eee" }}>
<div className="container py-5 h-100">
<div className="row d-flex justify-content-center align-items-center h-100">
<div className="col-xl-10">
<div className="card rounded-3 text-black">
<div className="row g-0">
<div className="col-lg-6">
<div className="card-body p-md-5 mx-md-4">
<Form onSubmit={handleSubmit}>
<p>Please login to your account</p>
<Form.Group className="mb-3" controlId="formBasicEmail">
<Form.Control
type="text"
name="email"
placeholder="Enter email"
onChange={handleChange}
/>
{errors?.email && <span>{errors.email}</span>}
</Form.Group>
<Form.Group
className="mb-3"
controlId="formBasicPassword"
>
<Form.Control
type="password"
name="password"
placeholder="Password"
onChange={handleChange}
/>
{errors?.password && <span>{errors.password}</span>}
</Form.Group>
<Form.Group
className="mb-3"
controlId="formBasicCheckbox"
>
<Form.Check type="checkbox" label="Check me out" />
</Form.Group>
<div className="d-grid gap-2 mb-3">
<Button
variant="primary"
type="submit"
className="gradient-custom-2"
size="md"
>
Submit
</Button>
</div>
</Form>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</section>
);
};
export default Login;
Now you can pass any custom function in your validation array :
const { validate, errors, setErrors } = FormValidation({
validationRules: {
email: [required, email],
password: [required, passwordPattern, customFunciton],
},
formInput,
});
const customFunciton = (formInputs, inputName) => ({
[inputName]: `This error is from my custom function`,
});

I would like to suggest the following library, it is not react-specific. However, it provides an easy syntax and handy methods to run form validation. This is the react validation example from the library's documentation https://www.simple-body-validator.com/react/validation-quickstart

Develop Reference

JavaScript is the programming language of the Web.