React Base Fiddle (JSX)

Starting point for creating JSFiddles with React.

HTML

<script src="https://unpkg.com/react@16/umd/react.development.js"></script>
<script src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"></script>
<div id="container">
    <!-- This element's contents will be replaced with your component. -->
</div>

Babel + JSX

class Hello extends React.Component {
	state = {hasError:false};
  
	onChange(event){
  	if(event.target.value.match(/^(?=.*[0-9])(?=.*[a-zA-Z])([a-zA-Z0-9]+)$/)){
    	this.setState({hasError:false});
    }else{
    	this.setState({hasError:true});
    }
  }
  
  render() {
    return <div>
      <input name="name" onChange={this.onChange.bind(this)}/>
      {this.state.hasError && <span>Error</span>}
    </div>;
  }
}

ReactDOM.render(
  <Hello name="World" />,
  document.getElementById('container')
);