how to sort an object in o 28n 29

1var maxSpeed = {
2    car: 300, 
3    bike: 60, 
4    motorbike: 200, 
5    airplane: 1000,
6    helicopter: 400, 
7    rocket: 8 * 60 * 60
8};
9var sortable = [];
10for (var vehicle in maxSpeed) {
11    sortable.push([vehicle, maxSpeed[vehicle]]);
12}
13
14sortable.sort(function(a, b) {
15    return a[1] - b[1];
16});
17
18//[["bike", 60], ["motorbike", 200], ["car", 300],
19//["helicopter", 400], ["airplane", 1000], ["rocket", 28800]]
20