(Much) faster tzdetect.js

gistfile1.txt

var tzdetect = {
  tzs: moment.tz.names(),
  matches: function(){
    return this.offsetToTimezone[(new Date()).getTimezoneOffset()];
  }
};

// compute (new Date()).getTimezoneOffset value for all timezones, store in tzdetect.offsetToTimezone
(function(tzdetect){
  var outp = {},
      tzs = tzdetect.tzs;
  
  for (var i = 0; i < tzs.length; ++i) {
    var m = moment().tz(tzs[i]),
        offset = m._offset;
    
    if (!outp.hasOwnProperty(offset)) outp[offset] = [];
    outp[offset].push(tzs[i]);
  }
  
  tzdetect.offsetToTimezone = outp;
})(tzdetect);