It's the same question as here, but I don't understand the answer. So, my question is about the answer.
The answer is
Your react.js file/module isn't exposing the variables React and ReactDOM you instantiate. In node, you make these methods public by modifying the module.exports object like so:
module.exports = { React: React, ReactDOM: ReactDOM }
Finally, my question is: Where do "you make these methods public"?
You are making these methods public by defining them on the module.exports property. For instance, say you have a file reactExports.js with
var iWontGetThere = 'I am in this module only';
module.exports = { React: React, ReactDOM: ReactDOM }
now in another file, you can require these methods and use them, like so:
var React = require('reactExports').React;
var SweetComponent = React.createClass({
render: function() {
return (
<div>React is cool and I can use it in here!</div>
);
}
});
module.exports = SweetComponent;
Now imagine you want to render SweetComponent in another component. If I hadn't written module.exports = SweetComponent, requiring this module in another component would have no effect as all as you would be importing an empty object {}.
Let's say I tried to console.log(React.iWontGetThere); What would happen? I would get a reference error, as it was not exported with the contents of reactExports.js-it only exists in that module, but it is not exposed.
This is a contrived example, but the interesting story here is the ability to bring in encapsulated modules. I suggest reading more about node modules here and checking out this answer as well. and making some examples to get the hang of it.
tl;dr: defining variables and not having a module.exports = some_value statement then requiring that same file will default to an empty object.
