Compare ISO 8601 date strings in javascript

I want to compare ISO 8601 dates in javascript as strings instead of making Date objects for each string and comparing objects.

var date_array = ['2012-10-01','2012-11-27','2012-12-23'];
console.log(date_array[0] < date_array[1])  // gives true
console.log(date_array[1] > date_array[2])  // gives false

My reason for doing this is I believe string comparisons should be faster than making objects for each date string and comparing objects.

These comparisons seem to work as expected in some browsers. Can I expect this sort of alphabetical lexicographic string comparison to work in all browsers? Is this method of date comparison actually faster than using Date objects?