moment.parseZone(String)
Moment normally interprets input times as local times (or UTC times if moment.utc() is used). However, often the input string itself contains time zone information. #parseZone parses the time and then sets the zone according to the input string.
moment.parseZone("2013-01-01T00:00:00-13:00").utcOffset(); // -780 ("-13:00" in total minutes)
moment.parseZone is equivalent to parsing the string and using moment#utcOffset to parse the zone.
var s = "2013-01-01T00:00:00-13:00";
moment(s).utcOffset(s);
Note: this method only works for a single string argument, not a string and format.