vDom_extendStyles.js

function extend(base, derivative){
  for(var i in base)
    if(!derivative[i])
      derivative[i] = base[i]
  return derivative
}

var base = {
  color: '#555',
  fontSize: '2em'
}

var box = extend(base, {
  padding: '10px',
  backgroundColor: '#ddd'
})

function Hello(name, styles){
  return ["div", {style:styles}, "Hello " + name]
}

ReactDOM.render(
  React.createElement.apply(
    this, Hello("World", box)
   ),
  document.getElementById('container')
);