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

In ES7+ (ES2016) you can use the experimental function bind syntax operator :: to bind. It is a syntactic sugar and will do the same as Davin Tryon's answer.

You can then rewrite this.delta = this.delta.bind(this); to this.delta = ::this.delta;

---

For ES6+ (ES2015) you can also use the ES6+ arrow function (=>) to be able to use this.

delta = () => {
    this.setState({
        count : this.state.count + 1
    });
}

Why ? From the Mozilla doc :

Until arrow functions, every new function defined its own this value [...]. This proved to be annoying with an object-oriented style of programming.

Arrow functions capture the this value of the enclosing context [...]