event_saver_POC.js

var templatePayload = {
    "account_id": 'account123',
    "visitors": [{
        "visitor_id": null,
        "attributes": {},
        "snapshots": [{
            "decisions": [],
            "events": []
            /*
            https://developers.optimizely.com/x/events/api/index.html
            Event { 
              "entity_id": "123456",
              "key": "test_event",
              "timestamp": 1540996187279,
              "revenue": 10000,
              "uuid": "2314324123"
            }
            */
        }]
    }],
    "anonymize_ip": true,
    "client_name": "Optimizely/client-side-event-tracker",
    "client_version": "1.0.0",
    "enrich_decisions": true
}

var buildPayload = function (visitorId, events) {
    events = events || [];
    // enrich event data with required data
    events = events.map(function (evt) {
        return Object.assign(evt, {
            uuid: evt.uuid || Math.random().toString(36).substr(2, 10),
            timestamp: evt.timestamp || (new Date).getTime()
        });
    });
    var sendPayload = Object.assign({}, templatePayload, { visitors: [{ attributes: [], visitor_id: visitorId, snapshots: [{ decisions: [], events: events }] }] })
    return sendPayload;
}

var trackEvent = function () {
    var payload = buildPayload.apply(null, arguments);
    return fetch('https://logx.optimizely.com/v1/events', {
        method: 'post',
        body: JSON.stringify(payload)
    }).then(function (response) {
        if (response.status > 199 && response.status < 300) return Promise.resolve(response);
        return Promise.reject(response);
    });
}

function getCookie(name) {
    var match = document.cookie.match(name + '=([^;]*)');
    return match ? match[1] : undefined;
};

function getUrlParameter(sParam) {
    var sPageURL = window.location.search.substring(1),
        sURLVariables = sPageURL.split('&'),
        sParameterName,
        i;

    for (i = 0; i < sURLVariables.length; i++) {
        sParameterName = sURLVariables[i].split('=');

        if (sParameterName[0] === sParam) {
            return sParameterName[1] === undefined ? true : decodeURIComponent(sParameterName[1]);
        }
    }
};

var session_data = JSON.parse(window.sessionStorage.getItem('optly_data'))

if(session_data){
    var data = session_data
}else{
    var data = window.optimizely.get('data');
    window.sessionStorage.setItem('optly_data', JSON.stringify(data));
}

var endUserId = getCookie('optimizelyEndUserId');
var topLevel = window.location.hostname.split('.').slice(-2).join('.')

var tags = []
for (var event in data.events) {
    if (data.events[event].eventType === 'click') {
        tags.push({ id: event, selector: data.events[event].eventFilter.selector })
    }
}

tags.forEach(function(obj) {
    let el = document.querySelector(obj.selector)

        if (el && el.href) {
            el.href += (el.href.split('?')[1] ? '&' : '?') + `event=${obj.id}`;
            el.href += (el.href.split('?')[1] ? '&' : '?') + `opt_id=${endUserId}`;
        }
    
})

if(window.location.href.indexOf('opt_id') !== -1 && window.location.href.indexOf('event') !== -1){
    let newId = getUrlParameter('opt_in');
    let event = getUrlParameter('event');
    trackEvent(newId, [{
        "entity_id": event
    }])
        .then(function (success) {
            console.log('Success', success);
        }, function (err) {
            console.log('Error', err);
        });
    
}