Reactjs - Form validation - reactjs

Question

Can anybody help me, I'm really struggling with the validation form in React, I was trying also with some library but I'm doing something wrong.
I want to validate both to be required and number to be a number.
class Hello extends React.Component {
constructor() {
super();
this.state = {
firstname: '',
number: '',
};
}
onChange = (event) => {
this.setState({ [event.target.name]: event.target.value });
}
onSubmit = (event) => {
event.preventDefault();
console.log('Submited');
}
render() {
return (
<div>
<form className="form-horizontal" onSubmit={this.onSubmit}>
<div className="form-group">
<label className="col-sm-2 control-label">Name</label>
<div className="col-sm-10">
<input type="text" name="firstname" className="form-control" onChange={this.onChange} placeholder="Firstname" />
</div>
</div>
<div className="form-group">
<label className="col-sm-2 control-label">Number</label>
<div className="col-sm-10">
<input type="text" name="number" className="form-control" onChange={this.onChange} placeholder="Number" />
</div>
</div>
<div className="form-group">
<div className="col-sm-offset-2 col-sm-10">
<button type="submit" className="btn btn-success">Submit</button>
</div>
</div>
</form>
<h3>{this.state.firstname}</h3>
<h3>{this.state.number}</h3>
</div>
);
}
}