js: sort_by function

gistfile1

// reusable sort functions, and sort by any field
// UsagesSort by price high to low
// homes.sort(sort_by('price', true, parseInt));
// Sort by city, case-insensitive, A-Z
// homes.sort(sort_by('city', false, function(a){return a.toUpperCase()}));

var sort_by = function(field, reverse, primer){
   var key = function (x) {return primer ? primer(x[field]) : x[field];};
   return function (a,b) {
       var A = key(a), B = key(b);
       return (((A < B) ? -1 :
               (A > B) ? +1 : 0)) * [-1,1][+!!reverse];
   };
};