Why doesn't React code work after some changes towards es6?

Question

JavaScript

I tried to write in React using the examples here - it worked.
Now I tried to rewrite it a little closer to ES6 - it doesn't work.
Where did I mess up?

Answer 1

It should be something like this
. The main problem is that getInitialState is replaced with a constructor and there is no autobinding in the ES6 syntax, so either use .bind(this) or arrow functions:

handleChange = (e) => {
    this.setState({val: e.target.value});
  }

  tick = () => {
    this.setState({
      first: new Date() - this.state.start
    });
  }