This usually means that the user mixed up our lowercase/uppercase naming convention; see https://github.com/facebook/react/pull/3429#issuecomment-85166440.

We could add a message like

> Warning: The tag <commentBox> is unrecognized in this browser. If you meant to render a React component, start its name with an uppercase letter.

We'd check this only once per tag and only in development mode.

return tagName.indexOf('-') >= 0 || props.is != null;
}
var globalIdCounter = 1;
/**
 * Creates a new React class that is idempotent and capable of containing other
 * React components. It accepts event listeners and DOM properties that are
 * valid according to `DOMProperty`.
 *
 *  - Event listeners: `onClick`, `onMouseDown`, etc.
 *  - DOM properties: `className`, `name`, `title`, etc.
 *
 * The `style` property functions differently from the DOM API. It accepts an
 * object mapping of style properties to values.
 *
 * @constructor ReactDOMComponent
 * @extends ReactMultiChild
 */
function ReactDOMComponent(element) {
  var tag = element.type;
  this._currentElement = element;
  this._tag = tag.toLowerCase();
  this._namespaceURI = null;
  this._renderedChildren = null;
  this._hostNode = null;
  this._hostParent = null;
  this._rootNodeID = 0;
  this._domID = 0;