code: function(x){
          if(x<2) return false;
          for(var i=0; i<primos.length; i++){
              var divisor=primos[i];
              if(x % divisor ==0){
                  return false;
              }
          }
          primos.push(x);
          return true;
      }
docs: por chrome bug segun: http://stackoverflow.com/questions/3880381/xmlhttprequest-responsetext-while-loading-readystate-3-in-chrome