React uncaught reference error: exports is not defined - ruby-on-rails

Question

I am trying to add React to an existing Rails 5.1 application, but I'm getting this error: Uncaught ReferenceError: exports is not defined.
I'm using webpacker. This is the contents of my application.js file:
//= require react
//= require react_ujs
//= require components
In my components directory, I have the file register.jsx:
class Register extends React.Component {
render(){
return(
<div>
<h1>Register a Group</h1>
</div>
)
}
}
export default Register
This file processes to this, as viewed in Chrome developer tools:
Object.defineProperty(exports, "__esModule", {
value: true
});
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 _get = function get(_x, _x2, _x3) { var _again = true; _function: while (_again) { var object = _x, property = _x2, receiver = _x3; _again = false; if (object === null) object = Function.prototype; var desc = Object.getOwnPropertyDescriptor(object, property); if (desc === undefined) { var parent = Object.getPrototypeOf(object); if (parent === null) { return undefined; } else { _x = parent; _x2 = property; _x3 = receiver; _again = true; desc = parent = undefined; continue _function; } } else if ("value" in desc) { return desc.value; } else { var getter = desc.get; if (getter === undefined) { return undefined; } return getter.call(receiver); } } };
function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }
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; }
// import React from 'react';
var Register = (function (_React$Component) {
_inherits(Register, _React$Component);
function Register() {
_classCallCheck(this, Register);
_get(Object.getPrototypeOf(Register.prototype), "constructor", this).apply(this, arguments);
}
_createClass(Register, [{
key: "render",
value: function render() {
return React.createElement(
"div",
null,
React.createElement(
"h1",
null,
"Register a Group"
)
);
}
}]);
return Register;
})(React.Component);
exports["default"] = Register;
module.exports = exports["default"];
The uncaught reference is being thrown at the very first line.
Any ideas are greatly appreciated!

Answer 1

React should be loaded from your application pack in app/javascripts/packs/application.js, not from app/assets/javascripts/application.js, as the default JavaScript compressor that Sprockets uses doesn't support ES6.
Your React components should be referenced from app/javascripts/components as well.
Also make sure you're importing React correctly in your component files:
import React from 'react-dom'
export default class Register extends React.Component {
render() {
return (
<div>
<h1>Register a Group</h1>
</div>
)
}
}