function getSelection(node) {
	  if ('selectionStart' in node && ReactInputSelection.hasSelectionCapabilities(node)) {
	    return {
	      start: node.selectionStart,
	      end: node.selectionEnd
	    };
	  } else if (window.getSelection) {
	    var selection = window.getSelection();
	    return {
	      anchorNode: selection.anchorNode,
	      anchorOffset: selection.anchorOffset,
	      focusNode: selection.focusNode,
	      focusOffset: selection.focusOffset
	    };
	  } else if (document.selection) {
	    var range = document.selection.createRange();
	    return {
	      parentElement: range.parentElement(),
	      text: range.text,
	      top: range.boundingTop,
	      left: range.boundingLeft
	    };
	  }
	}
Get an object which is a unique representation of the current selection.

The return value will not be consistent across nodes or browsers, but
two identical selections on the same node will return identical objects.

@param {DOMElement} node
@return {object}