dom vs obj prop store.js

var i,n=3000, j;
var a=document.getElementsByTagName('li'), m = a.length, v;

for(j = 0 ; j < m ; ++j)
  a[j].b = {};

console.time("1");
for(i = 0 ; i < n ; ++i)
  for(j = 0 ; j < m ; ++j)
    (v = a[j]).x = 1, v.y = 1, v.z = v.x, v.g = v.x + v.y + v.z;
console.timeEnd("1");

console.time("2");
for(i = 0 ; i < n ; ++i)
  for(j = 0 ; j < m ; ++j)
    (v = a[j].b).x = 1, v.y = 1, v.z = v.x, v.g = v.x + v.y + v.z;
console.timeEnd("2");


/*
ff 3.6 n = 3000
2: 2694
1: 2792
1: 2877
2: 2552

chrome 4 n = 3000
1: 2916
2: 2845
2: 2952
1: 2759

opera 10.51 n = 3000
2: 1736
1: 1614
1: 1664
2: 1649

ie n = 500
2: 1191
1: 2334
1: 2424
2: 1101
*/