code: function syncSetState (newState) {
    // Mutation is faster and should be safe here.
    this.state = assign(
      this.state,
      isFunction(newState) ?
        newState(this.state, this.props) :
        newState
    );
  }
docs: A synchronous replacement for React's `setState` method.
  
  @param      {Function|Object}  newState  An object containing new keys/values
  or a function that will provide the same.
  
  @returns    {undefined}                  No return value.