https://flowstay.ai/js/fd-exp.js

1/* FlowDirect Growth Engine — copy-experiment harness (hotel #0).
2 * Elements opt in with data-exp="<name>". For each, we read the PostHog
3 * feature flag "exp-<name>"; if its payload JSON contains {"text": "..."}
4 * the element's text is swapped. PostHog records exposure automatically
5 * ($feature_flag_called), so experiment results attribute themselves.
6 *
7 * Anti-flicker: tagged elements are hidden until flags resolve, with an
8 * 800ms fail-open timeout (control shows if PostHog is slow/blocked).
9 * Include AFTER the PostHog snippet: <script src="/js/fd-exp.js" defer></script>
10 */
11(function () {
12  "use strict";
13  try {
14    var els = document.querySelectorAll("[data-exp]");
15    if (!els.length) return;
16
17    var style = document.createElement("style");
18    style.textContent = "[data-exp]:not([data-exp-ready]){visibility:hidden}";
19    document.head.appendChild(style);
20
21    var done = false;
22    function reveal() {
23      if (done) return;
24      done = true;
25      document.querySelectorAll("[data-exp]").forEach(function (el) {
26        el.setAttribute("data-exp-ready", "1");
27      });
28    }
29
30    function apply() {
31      try {
32        els.forEach(function (el) {
33          var key = "exp-" + el.getAttribute("data-exp");
34          var variant = window.posthog.getFeatureFlag(key);
35          if (variant && variant !== "control") {
36            var payload = window.posthog.getFeatureFlagPayload(key);
37            if (payload && typeof payload.text === "string") {
38              el.textContent = payload.text; // textContent only: no HTML injection
39            }
40          }
41        });
42      } catch (e) { /* fail open to control */ }
43      reveal();
44    }
45
46    if (window.posthog && typeof window.posthog.onFeatureFlags === "function") {
47      window.posthog.onFeatureFlags(apply);
48    }
49    setTimeout(reveal, 800); // fail-open: never hold the page hostage
50  } catch (e) {
51    try {
52      document.querySelectorAll("[data-exp]").forEach(function (el) {
53        el.setAttribute("data-exp-ready", "1");
54      });
55    } catch (e2) { /* noop */ }
56  }
57})();