cannot read property 27setstate 27 of undefined

1class Counter extends React.Component {
2    constructor(props) {
3      super(props);
4
5      this.state = {
6          count : 1
7      };
8
9      this.delta = this.delta.bind(this);
10	}
11
12    delta() {
13        this.setState({
14            count : this.state.count++
15        });
16    }
17
18    render() {
19        return (
20            <div>
21                <h1>{this.state.count}</h1>
22                <button onClick={this.delta}>+</button>
23            </div>
24        );
25    }
26}

1//  way #1 - recommended
2// puting .bind(this) after using the reference 
3
4	<input onChange={this.onInputChange.bind(this)} placeholder="First Name" />
5  
6// way #2
7// adding this line for each method you use
8  
9  constructor(){
10	this.onInputChange = this.onInputChange.bind(this)
11  }
12