Javascript if (x + y + z <=10) does not work well

I have 3 dice, I want when the number of dice <=10, will do something. And the number of dice >=11 will do another something so i try this code;

var x= Math.floor(Math.random() * 6)+1; 
var y= Math.floor(Math.random() * 6)+1;
var z= Math.floor(Math.random() * 6)+1;

 if(x+y+z <=10){
  // do something
 }else
  { // do another 
  }

And that code didn't work well. eg: x =2 y =4 z=6 , it will do both.