React.js tips.

React can either render HTML tags (strings) or React components (classes).

To render an HTML tag, just use lower-case tag names in JSX:

var myDivElement = <div className="foo" />;
ReactDOM.render(myDivElement, document.getElementById('example'));

To render a React Component, just create a local variable that starts with an upper-case letter:

var MyComponent = React.createClass({/*...*/});
var myElement = <MyComponent someProperty={true} />;
ReactDOM.render(myElement, document.getElementById('example'));

React's JSX uses the upper vs. lower case convention to distinguish between local component classes and HTML tags.