HTML5 Validation with React.

React_HTML5_Form_Field_Level_Validation.js

import React, { Component } from 'react';

class FormTest extends Component {
    constructor(props) {
        super(props);
        this.state = {
            username: {
                value: '',
                valid: false,
                errorMessage: ''
            },
            password: {
                value: '',
                valid: false,
                errorMessage: ''
            },
            form: {
                valid: false
            }
        }
    }

    onInputChange(event) {
        const targetName = event.target.name;
        const targetValue = event.target.value;
        const el = this.refs[targetName];
        this.setState({
            [targetName]: {
                value: targetValue,
                valid: el.validity.valid,
                errorMessage: el.validity.valueMissing ? `${targetName} is required` : el.validationMessage
            },
            form: {
                valid: this.form.checkValidity()
            }
        });
    }

    onSubmit(event) {

    }

    returnErrorMessage(inputType) {
        let obj = this.state[inputType];
        return (
            <span>
                {!obj.valid && obj.errorMessage}
            </span>
        );
    }

    render() {
        return (
            <div>
                <div>Form Test</div>
                <form onSubmit={this.onSubmit.bind(this)} ref={form => this.form = form}>
                    <input ref='username' type="text" value={this.state.username.value} onChange={this.onInputChange.bind(this)} name='username' required/>
                    {this.returnErrorMessage('username')}
                    <br/><br/>

                    <input ref='password' type="password" value={this.state.password.value} onChange={this.onInputChange.bind(this)} name='password' required/>
                    {this.returnErrorMessage('password')}
                    <br/><br/>
                    <button type="submit" disabled={!this.state.form.valid}>Submit</button>
                </form>
            </div>
        );
    }
}

export default FormTest;