https://www.interfunnels.com/website/templates/tracking_params.js

1/**
2 * Facebook Tracking Parameters Capture & Persistence (Funnel Module)
3 * 
4 * Captures URL parameters on first touch and stores them in localStorage
5 * for use in Facebook Conversions API calls.
6 * 
7 * Captured parameters:
8 * - fbclid (Facebook Click ID)
9 * - fbp (Facebook Browser ID from cookie)
10 * - fbc (Facebook Click - auto-generated from fbclid)
11 * - gclid, msclkid, ttclid, twclid (Other platform click IDs)
12 * - utm_* (All UTM parameters)
13 * - Custom parameters (any starting with 'custom_')
14 * 
15 * Browser compatible: No ES6 (no const/let/arrow/for-of)
16 */
17
18(function() {
19    'use strict';
20
21    /**
22     * Get cookie value by name
23     */
24    function getCookie(name) {
25        var nameEQ = name + "=";
26        var ca = document.cookie.split(';');
27        for (var i = 0; i < ca.length; i++) {
28            var c = ca[i];
29            while (c.charAt(0) === ' ') c = c.substring(1, c.length);
30            if (c.indexOf(nameEQ) === 0) return c.substring(nameEQ.length, c.length);
31        }
32        return null;
33    }
34
35    /**
36     * Generate Facebook Click parameter (fbc) from fbclid
37     * Format: fb.1.{timestamp}.{fbclid} — timestamp must be first-click time
38     */
39    function generateFbc(fbclid, timestamp) {
40        if (!fbclid) return null;
41        if (!timestamp) {
42            timestamp = Math.floor(Date.now() / 1000);
43        }
44        return 'fb.1.' + timestamp + '.' + fbclid;
45    }
46
47    function isValidFbp(value) {
48        return value && String(value).indexOf('fb.1.') === 0;
49    }
50
51    function isValidFbc(value) {
52        return value && /^fb\.1\.\d+\..+/.test(String(value));
53    }
54
55    /**
56     * Get current tracking parameters from localStorage
57     */
58    function getStoredParams() {
59        try {
60            var stored = localStorage.getItem('tracking_params');
61            return stored ? JSON.parse(stored) : {};
62        } catch (e) {
63            return {};
64        }
65    }
66
67    /**
68     * Save tracking parameters to localStorage
69     */
70    function saveParams(params) {
71        try {
72            localStorage.setItem('tracking_params', JSON.stringify(params));
73        } catch (e) {
74            // localStorage not available
75        }
76    }
77
78    /**
79     * Parse URL query string into key-value pairs (no URLSearchParams needed)
80     */
81    function parseQueryString(search) {
82        var params = {};
83        var queryString = search.substring(1); // remove leading ?
84        if (!queryString) return params;
85        
86        var pairs = queryString.split('&');
87        for (var i = 0; i < pairs.length; i++) {
88            var pair = pairs[i].split('=');
89            if (pair[0]) {
90                var key = decodeURIComponent(pair[0]);
91                var value = pair.length > 1 ? decodeURIComponent(pair[1]) : '';
92                params[key] = value;
93            }
94        }
95        return params;
96    }
97
98    /**
99     * Capture and persist tracking parameters from URL
100     */
101    function captureTrackingParams() {
102        try {
103            var urlParams = parseQueryString(window.location.search);
104            var currentParams = getStoredParams();
105            var updated = false;
106
107            // List of parameters to capture
108            var paramsToCapture = [
109                'fbclid',   // Facebook Click ID
110                'gclid',    // Google Click ID
111                'msclkid',  // Microsoft Click ID
112                'ttclid',   // TikTok Click ID
113                'twclid',   // Twitter Click ID
114                'li_fat_id', // LinkedIn First Party Ad Tracking
115                'ScCid',    // Snapchat Click ID
116                'utm_source',
117                'utm_medium',
118                'utm_campaign',
119                'utm_term',
120                'utm_content',
121                'utm_id'
122            ];
123
124            // Capture standard parameters
125            for (var i = 0; i < paramsToCapture.length; i++) {
126                var param = paramsToCapture[i];
127                var value = urlParams[param];
128                if (value && value !== currentParams[param]) {
129                    currentParams[param] = value;
130                    updated = true;
131                }
132            }
133
134            // Capture any custom parameters (custom_*)

135            for (var key in urlParams) {
136                if (urlParams.hasOwnProperty(key) && key.indexOf('custom_') === 0) {
137                    if (urlParams[key] !== currentParams[key]) {
138                        currentParams[key] = urlParams[key];
139                        updated = true;
140                    }
141                }
142            }
143
144            // Capture fbclid on first touch; preserve first-click fbc timestamp
145            if (urlParams.fbclid && urlParams.fbclid !== currentParams.fbclid) {
146                currentParams.fbclid = urlParams.fbclid;
147                currentParams.fbc_ts = Math.floor(Date.now() / 1000);
148                currentParams.fbc = null;
149                updated = true;
150            } else if (urlParams.fbclid && !currentParams.fbclid) {
151                currentParams.fbclid = urlParams.fbclid;
152                if (!currentParams.fbc_ts) {
153                    currentParams.fbc_ts = Math.floor(Date.now() / 1000);
154                }
155                updated = true;
156            }
157
158            // Prefer Meta _fbc cookie, else build fbc once from first-touch fbclid
159            var fbcCookie = getCookie('_fbc');
160            if (fbcCookie && isValidFbc(fbcCookie)) {
161                if (fbcCookie !== currentParams.fbc) {
162                    currentParams.fbc = fbcCookie;
163                    updated = true;
164                }
165            } else if (currentParams.fbclid && !isValidFbc(currentParams.fbc)) {
166                if (!currentParams.fbc_ts) {
167                    currentParams.fbc_ts = Math.floor(Date.now() / 1000);
168                }
169                var builtFbc = generateFbc(currentParams.fbclid, currentParams.fbc_ts);
170                if (builtFbc !== currentParams.fbc) {
171                    currentParams.fbc = builtFbc;
172                    updated = true;
173                }
174            }
175
176            // Capture fbp from cookie (set by Facebook Pixel JS)
177            var fbpCookie = getCookie('_fbp');
178            if (fbpCookie && isValidFbp(fbpCookie) && fbpCookie !== currentParams.fbp) {
179                currentParams.fbp = fbpCookie;
180                updated = true;
181            }
182
183            // Capture referrer on first visit
184            if (!currentParams.ref && document.referrer) {
185                currentParams.ref = document.referrer;
186                updated = true;
187            }
188
189            // Add capture timestamp if this is first time
190            if (!currentParams._captured_at) {
191                currentParams._captured_at = new Date().toISOString();
192                updated = true;
193            }
194
195            // Save if anything changed
196            if (updated) {
197                saveParams(currentParams);
198            }
199        } catch (e) {
200            // Fail silently
201        }
202    }
203
204    /**
205     * Global function to retrieve tracking parameters
206     * Used by other scripts to get params for CAPI calls
207     */
208    window.getTrackingParams = function() {
209        captureTrackingParams();
210        return getStoredParams();
211    };
212
213    /**
214     * Global function to manually set a tracking parameter
215     */
216    window.setTrackingParam = function(key, value) {
217        try {
218            var params = getStoredParams();
219            params[key] = value;
220            saveParams(params);
221        } catch (e) {
222            // Fail silently
223        }
224    };
225
226    /**
227     * Global function to clear all tracking parameters
228     */
229    window.clearTrackingParams = function() {
230        try {
231            localStorage.removeItem('tracking_params');
232        } catch (e) {
233            // Fail silently
234        }
235    };
236
237    // Run immediately when script loads
238    captureTrackingParams();
239
240    // Re-capture after Meta Pixel JS sets _fbp / _fbc cookies
241    setTimeout(captureTrackingParams, 1500);
242    setTimeout(captureTrackingParams, 3500);
243
244    // Also run when DOM is ready (in case cookies load later)
245    if (document.readyState === 'loading') {
246        document.addEventListener('DOMContentLoaded', captureTrackingParams);
247    }
248
249})();