gistfile1.js

   var ZipRanges = {
     ranges: {
       'AK':'99500-99929',
       'AL':'35000-36999',
       'AR':'71600-72999,75502-75505'
       // ...
     },
     toState: function(zip_code) {
       var z = parseInt(zip_code);
       var s = null;
       
       $.each(ZipRanges.ranges, function(state, zip_range) {
         var chunks = zip_range.split(/\,/);
         $.each(chunks, function(i, chunk) {
           var range = chunk.split(/\-/);
           var start = parseInt(range[0]);
           var finish = parseInt(range[1]);
           if ((start <= z) && (finish >= z)) {
             s = state;
             return false;
           }
         });
         if (s != null) return false;
       });
       if (s != null) return s;
       return "Invalid Zip";
     }
   }