d = new Date ; 
for (i = count; i-- ;){ 
     a.concat(b); 
} 
r[0] = new Date - d; 

d = new Date ; 
for (i = count; i-- ;){ 
     r.push.apply(a,b); 
     //a = [1,2,3] ; 
} 
r[1] = new Date - d; 

alert(r);