Edit in JSFiddle

changeTurn: function() {

	  this.setState(function(prevState) {
	    	var data = prevState.data;
	    	return {
	    		  data: update(data, {
			    	    gameTurn: {$apply: gameturn => 3 - gameturn},
			    	    player1: {turn: {$apply: value => !value}},
			    	    player2: {turn: {$apply: value => !value}},
	    		  })
	    	}
	  });	  

	},