speed/slice.vs.concat.html

   1 <script type="text/javascript">
   2 (function(){
   3         // Conclusions:
   4         // slice() is a little faster than concat() except on Chrome
   5         // This clone() is slower on FF & IE but takes 50% on Safari & Chrome
   6
   7         var SIZE = 1e4,
   8                 LOOPS = 500;
   9
  10         var arr = new Array(SIZE);
  11         for ( var i=arr.length-1; i >= 0; --i )
  12                 arr[i] = 0;
  13
  14         var t = new Date;
  15         for ( i=0; i < LOOPS; i++ )
  16                 arr.slice(0);
  17         var tslice = new Date - t;
  18
  19         t = new Date;
  20         for ( i=0; i < LOOPS; i++ )
  21                 arr.concat();
  22         var tconcat = new Date - t;
  23
  24         // clone() is just to see how fast built-ins are
  25         t = new Date;
  26         for ( i=0; i < LOOPS; i++ )
  27                 clone(arr);
  28         var tclone = new Date - t;
  29
  30         alert([
  31                 'slice:'+tslice,
  32                 'concat:'+tconcat,
  33                 'clone:'+tclone
  34         ].join('\n'));
  35
  36
  37         function clone(arr){
  38                 var i = arr.length,
  39                         copy = new Array(i);
  40
  41                 while (i--)
  42                         copy[i] = arr[i];
  43
  44                 return copy;
  45         }
  46 })();
  47 </script>