WelcomeComp.js

class WelcomeComp extends React.Component {
  constructor(props) {
    super(props);
    this.state = { name: '' }
    if (props.name) this.state = { name: props.name };
  }

  updateName = name => this.setState({ name })

  render() {
    return (
      <p>I am a React Component. Hello {this.state.name}</p>
    )
  }
}

// This is a compiled(transpiled) version of the above code, which you actually go into the HTML.
/*
'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; }; }();

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 WelcomeComp = function (_React$Component) {
  _inherits(WelcomeComp, _React$Component);

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

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

    _this.updateName = function (name) {
      return _this.setState({ name: name });
    };

    _this.state = { name: '' };
    if (props.name) _this.state = { name: props.name };
    return _this;
  }

  _createClass(WelcomeComp, [{
    key: 'render',
    value: function render() {
      return React.createElement(
        'p',
        null,
        'I am a React Component. Hello ',
        this.state.name
      );
    }
  }]);

  return WelcomeComp;
}(React.Component);
*/