gistfile1.js

>>> var C = React.createClass({
      getInitialState: function() {
        return {1: 2}
      },
      render: function() {
        return React.createElement('div', 'test')
      }
    })
undefined
>>> var original = C.type.prototype.getInitialState
undefined
>>> C.type.prototype.getInitialState = function() {
      return Object.assign({3: 4}, original())
    }
function C.type.prototype.getInitialState()
>>> var c = React.render(React.createElement(C), document.body)
undefined
>>> c.state
Object { 1: 2, 3: 4 }