Code for doing Register Once traits using Segment.com using a Cookie, this mimics the registerOnce function of MixPanel

fealty_segmentio_tracking.js

var _optly = { 
  updateQueryString: function(key, value, url) {
    if (!url) url = window.location.href;
    var re = new RegExp("([?|&])" + key + "=.*?(&|#|$)(.*)", "gi");

    if (re.test(url)) {
        if (typeof value !== 'undefined' && value !== null)
            return url.replace(re, '$1' + key + "=" + value + '$2$3');
        else {
            var hash = url.split('#');
            url = hash[0].replace(re, '$1$3').replace(/(&|\?)$/, '');
            if (typeof hash[1] !== 'undefined' && hash[1] !== null) 
                url += '#' + hash[1];
            return url;
        }
    }
    else {
        if (typeof value !== 'undefined' && value !== null) {
            var separator = url.indexOf('?') !== -1 ? '&' : '?',
                hash = url.split('#');
            url = hash[0] + separator + key + '=' + value;
            if (typeof hash[1] !== 'undefined' && hash[1] !== null) 
                url += '#' + hash[1];
            return url;
        }
        else
            return url;
    }
  },
  setCookie: function(c_name, value, exdays) {
        var exdate=new Date();
        exdate.setDate(exdate.getDate() + exdays);
        var c_value=escape(value) + 
          ((exdays==null) ? "" : ("; expires="+exdate.toUTCString()));
        document.cookie=c_name + "=" + c_value;
  },
  getCookie: function(name) {
    var parts = document.cookie.split(name + "=");
    if (parts.length == 2) return parts.pop().split(";").shift();
  },
  delCookie: function(c_name) {
        var exdate=new Date();
        exdate.setDate(exdate.getDate() - 365);
        var c_value=" ; expires="+exdate.toUTCString();
        document.cookie=c_name + "=" + c_value;
  },
  getParameterByName: function(name) {
    name = name.replace(/[\[]/, "\\\[").replace(/[\]]/, "\\\]");
    var regex = new RegExp("[\\?&]" + name + "=([^&#]*)"),
        results = regex.exec(location.search);
    return results == null ? "" : decodeURIComponent(results[1].replace(/\+/g, " "));
  }
}

window.analytics.ready(function() {
	// set configs
	mixpanel.set_config({
		"track_links_timeout": 750
	});
});

// identify global page variables
var identifyVars = {
	"Page": window.location.href,
	"Page Title": "Your Page Name",
};

// register one time variables, check cookie
if (_optly.getCookie('fealty_segment_registeronce') != 1) {
	identifyVars["Landing Page"] = window.location.href;
	identifyVars["Landing Page Title"] = "Your Page Name";
	
	// save cookie for 365 days
	_optly.setCookie('fealty_segment_registeronce', 1, 365);
}

// save traits using .identify
window.analytics.identify(identifyVars);