How to write in React?

Question

JavaScript

I started learning react, but I don't know how to format the code better?

let Block1 = React.createClass({ // вариант №1
  render () {
    return <h2>Hello world! (1)</h2>;
  }
});

const Block2 = React.createClass({ // вариант №2
  render: () => <h2>Hello world! (2)</h2>
});

var Block3 = React.createClass({ // вариант №3
  render: function() {
    return <h2>Hello world! (3)</h2>;
  }
});

Answer 1

throw away createClass and use ES6 classes here