Format Moment Duration easily
function (duration, format) {
//Setup time
var hours = duration.hours(),
minutes = duration.minutes(),
seconds = duration.seconds();
//Iterate the format
formatStr = format;
//Replace format keys
formatStr = formatStr.replace(/hh:/, hours > 0 ? hours + ":" : '');
formatStr = formatStr.replace(/mm:/, minutes > 0 ? minutes + ":" : '');
formatStr = formatStr.replace(/ss/, seconds > 0 ? seconds : '0');
return formatStr;
};