React - uncaught TypeError: Cannot read property 'setState' of undefined

Question

I am getting the following error

Uncaught TypeError: Cannot read property \'setState\' of undefined

even after binding delta in

Answer 1

There are two solutions of this issue:

The first solution is add a constructor to your component and bind your function like bellow:

constructor(props) {
        super(props);

        ...

        this.delta = this.delta.bind(this);
    }

So do this:

this.delta = this.delta.bind(this); 

Instead of this:

this.delta.bind(this);

The second solution is to use an arrow function instead:

delta = () => {
       this.setState({
           count : this.state.count++
      });
   }

Actually arrow function DOES NOT bind it’s own this. Arrow Functions lexically bind their context so this actually refers to the originating context.

For more information about bind function:

Bind function Understanding JavaScript Bind ()

For more information about arrow function:

Javascript ES6 — Arrow Functions and Lexical this