Nashhorn ECMAException for renderToString with invalid ReactElememt

Question

• JDK 8
• React 0.13.1

Getting the following error when using Nashorn to render a ReactJS component

Error: Invariant Violation: renderToString(): You must pass a valid ReactElement.

component.js

var Controller = React.createClass({
  render: function() {
    return (React.createElement("div",null,"Hello, World!"));
  }
});

var renderEventsComponentServer = function (eventList) {
  return React.renderToString(Controller);
};

From Java

Object html = nashorn.invokeFunction("renderEventsComponentServer", events);

This however works fine

var renderEventsComponentServer = function (eventList) {
  return React.renderToString(React.createElement("div",null,"Hello, World!"));
};

With result

<div data-reactid=".19jt6qowty6" data-react-checksum="-706801283">Hello, World!</div>

I'm obviously missing something fundamental about how ReactJS/Nashorns works.

These are the JS files being loaded

nashorn.eval(read("assets/js/react.js"));  
nashorn.eval(read("assets/js/react-dom.js"));  
nashorn.eval(read("assets/js/babel.min.js"));  
nashorn.eval(read("assets/js/axios.js"));  
nashorn.eval(read("assets/js/nashorn-polyfill.js"));  
nashorn.eval(read("assets/js/events.js"));

Answer 1

Using

return React.renderToString(React.createElement(Controller, null));

instead of

return React.renderToString(Controller);

did the trick.

component.js

var Controller = React.createClass({
  render: function() {
    return (React.createElement("div",null,"Hello, World!"));
  }
});

var renderEventsComponentServer = function (eventList) {
  return React.renderToString(React.createElement(Controller, null));
};

Nugget of info:

When I started trying to use ReactJS with Nashorn for SSR I downloaded the latest version of ReactJS which was throwing lots of errors, some deprecations that were removed altogether. I'm now using 0.13.1 which seems to be working as expected.