Is it possible to get the index you're sorting over in Underscore.js?

I'm using the JS library Underscore and in particular using the _.each and _.sortby library calls. I'm wondering if there's any possible way to get the index of the value within the iterator delegate _.sortBy([1, 4, 2, 66, 444, 9], function(num){ /*It'd be great to have access to the index in here */ return Math.sin(num); });