getCoordinates: function(){
  var dropMen = this.refs.targetDiv.getDOMNode();
  var specs = dropmen.getBoundingClientRect();
}

render: function(){
  return <div ref="targetDiv"></div>
}

Use ref with getDOMNode() to get the actual html.  
Using getBoundingClientRect() on the actual html will give you the width, height, etc.

Below:
specs =  ClientRect {} bottom: 269 height: 18 left: 797.546875 right: 1062.609375 top: 251 width: 265.0625__proto__: ClientRect

console.log(specs.bottom) will return 269

React:  Get width, height, and coordinates of a react object

javascript

JavaScript