React createClass?

1-source.js

import React from 'react'
import ReactDOM from 'react-dom';

class Counter extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      count: 1
    }
  }
  componentDidMount() {
    setInterval( ()=> {
      this.setState((prevState, props) => ({
        count: prevState.count + 1
      }))
    }, 1000)
  }
  render(){
    return (
      <h1>{this.state.count}</h1>
    )
  }
}

const root = document.createElement('div');
root.id = 'app';
document.body.appendChild(root);

ReactDOM.render(
  <Counter />,
  document.querySelector('#app')
);

2-generated-stage-2.js

'use strict';

var _createClass = function () { function defineProperties(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } } return function (Constructor, protoProps, staticProps) { if (protoProps) defineProperties(Constructor.prototype, protoProps); if (staticProps) defineProperties(Constructor, staticProps); return Constructor; }; }();

var _react = require('react');

var _react2 = _interopRequireDefault(_react);

var _reactDom = require('react-dom');

var _reactDom2 = _interopRequireDefault(_reactDom);

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

function _possibleConstructorReturn(self, call) { if (!self) { throw new ReferenceError("this hasn't been initialised - super() hasn't been called"); } return call && (typeof call === "object" || typeof call === "function") ? call : self; }

function _inherits(subClass, superClass) { if (typeof superClass !== "function" && superClass !== null) { throw new TypeError("Super expression must either be null or a function, not " + typeof superClass); } subClass.prototype = Object.create(superClass && superClass.prototype, { constructor: { value: subClass, enumerable: false, writable: true, configurable: true } }); if (superClass) Object.setPrototypeOf ? Object.setPrototypeOf(subClass, superClass) : subClass.__proto__ = superClass; }

var Counter = function (_React$Component) {
  _inherits(Counter, _React$Component);

  function Counter(props) {
    _classCallCheck(this, Counter);

    var _this = _possibleConstructorReturn(this, (Counter.__proto__ || Object.getPrototypeOf(Counter)).call(this, props));

    _this.state = {
      count: 1
    };
    return _this;
  }

  _createClass(Counter, [{
    key: 'componentDidMount',
    value: function componentDidMount() {
      var _this2 = this;

      setInterval(function () {
        _this2.setState(function (prevState, props) {
          return {
            count: prevState.count + 1
          };
        });
      }, 1000);
    }
  }, {
    key: 'render',
    value: function render() {
      return _react2.default.createElement(
        'h1',
        null,
        this.state.count
      );
    }
  }]);

  return Counter;
}(_react2.default.Component);

var root = document.createElement('div');
root.id = 'app';
document.body.appendChild(root);

_reactDom2.default.render(_react2.default.createElement(Counter, null), document.querySelector('#app'));

3-generated-stage-0.js

'use strict';

var _createClass = function () { function defineProperties(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } } return function (Constructor, protoProps, staticProps) { if (protoProps) defineProperties(Constructor.prototype, protoProps); if (staticProps) defineProperties(Constructor, staticProps); return Constructor; }; }();

var _react = require('react');

var _react2 = _interopRequireDefault(_react);

var _reactDom = require('react-dom');

var _reactDom2 = _interopRequireDefault(_reactDom);

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

function _possibleConstructorReturn(self, call) { if (!self) { throw new ReferenceError("this hasn't been initialised - super() hasn't been called"); } return call && (typeof call === "object" || typeof call === "function") ? call : self; }

function _inherits(subClass, superClass) { if (typeof superClass !== "function" && superClass !== null) { throw new TypeError("Super expression must either be null or a function, not " + typeof superClass); } subClass.prototype = Object.create(superClass && superClass.prototype, { constructor: { value: subClass, enumerable: false, writable: true, configurable: true } }); if (superClass) Object.setPrototypeOf ? Object.setPrototypeOf(subClass, superClass) : subClass.__proto__ = superClass; }

var Counter = function (_React$Component) {
  _inherits(Counter, _React$Component);

  function Counter(props) {
    _classCallCheck(this, Counter);

    var _this = _possibleConstructorReturn(this, (Counter.__proto__ || Object.getPrototypeOf(Counter)).call(this, props));

    _this.state = {
      count: 1
    };
    return _this;
  }

  _createClass(Counter, [{
    key: 'componentDidMount',
    value: function componentDidMount() {
      var _this2 = this;

      setInterval(function () {
        _this2.setState(function (prevState, props) {
          return {
            count: prevState.count + 1
          };
        });
      }, 1000);
    }
  }, {
    key: 'render',
    value: function render() {
      return _react2.default.createElement(
        'h1',
        null,
        this.state.count
      );
    }
  }]);

  return Counter;
}(_react2.default.Component);

var root = document.createElement('div');
root.id = 'app';
document.body.appendChild(root);

_reactDom2.default.render(_react2.default.createElement(Counter, null), document.querySelector('#app'));