Store the reason to reload

Rename firstTime to !reloadedBySelf.
coepDegrading and reloadedBySelf share the same storage item.
Document that coi.doReload() can use the storage item to see the reason to reload.

README.md

@@ -41,8 +41,8 @@ You can customize the behavior by defining a variable `coi` in the global scope
 window.coi = {
     // A function that is run to decide whether to register the SW or not.
     // You could for instance make this return a value based on whether you actually need to be cross origin isolated or not.
-    // The variable "firstTime" is false only if it has been reloaded by itself.
-    shouldRegister: () => firstTime,
+    // Using "!reloadedBySelf" you can avoid infinite loops of reloading.
+    shouldRegister: () => !reloadedBySelf,
     // If this function returns true, any existing service worker will be deregistered (and nothing else will happen).
     shouldDeregister: () => false,
     // A function that is run to decide whether to use "Cross-Origin-Embedder-Policy: credentialless" or not.
@@ -52,6 +52,7 @@ window.coi = {
     coepDegrade: () => true,
     // Override this if you want to prompt the user and do reload at your own leisure. Maybe show the user a message saying:
     // "Click OK to refresh the page to enable <...>"
+    // You can see window.sessionStorage.getItem("coiReloadedBySelf") for the reason to reload.
     doReload: () => window.location.reload(),
     // Set to true if you don't want coi to log anything to the console.
     quiet: false

coi-serviceworker.js

@@ -60,12 +60,13 @@ if (typeof window === 'undefined') {
 
 } else {
     (() => {
-        const firstTime = !window.sessionStorage.getItem("coiReloadedBySelf");
+        const reloadedBySelf = window.sessionStorage.getItem("coiReloadedBySelf");
         window.sessionStorage.removeItem("coiReloadedBySelf");
+        const coepDegrading = (reloadedBySelf == "coepdegrade");
 
         // You can customize the behavior of this script through a global `coi` variable.
         const coi = {
-            shouldRegister: () => firstTime,
+            shouldRegister: () => !reloadedBySelf,
             shouldDeregister: () => false,
             coepCredentialless: () => true,
             coepDegrade: () => true,
@@ -83,10 +84,6 @@ if (typeof window === 'undefined') {
         }
         const coepHasFailed = window.sessionStorage.getItem("coiCoepHasFailed");
 
-        // See if it is in degradation process using a volatile storage item.
-        const coepDegrading = window.sessionStorage.getItem("coiCoepDegrading");
-        window.sessionStorage.removeItem("coiCoepDegrading");
-
         if (controlling) {
             // Reload only on the first failure.
             const reloadToDegrade = coi.coepDegrade() && !(
@@ -99,8 +96,8 @@ if (typeof window === 'undefined') {
                     : coi.coepCredentialless(),
             });
             if (reloadToDegrade) {
-                window.sessionStorage.setItem("coiCoepDegrading", "true");
                 !coi.quiet && console.log("Reloading page to degrade COEP.");
+                window.sessionStorage.setItem("coiReloadedBySelf", "coepdegrade");
                 coi.doReload("coepdegrade");
             }
 
@@ -123,16 +120,17 @@ if (typeof window === 'undefined') {
             n.serviceWorker.register(window.document.currentScript.src).then(
                 (registration) => {
                     !coi.quiet && console.log("COOP/COEP Service Worker registered", registration.scope);
-                    window.sessionStorage.setItem("coiReloadedBySelf", "true");
 
                     registration.addEventListener("updatefound", () => {
                         !coi.quiet && console.log("Reloading page to make use of updated COOP/COEP Service Worker.");
+                        window.sessionStorage.setItem("coiReloadedBySelf", "updatefound");
                         coi.doReload();
                     });
 
                     // If the registration is active, but it's not controlling the page
                     if (registration.active && !n.serviceWorker.controller) {
                         !coi.quiet && console.log("Reloading page to make use of COOP/COEP Service Worker.");
+                        window.sessionStorage.setItem("coiReloadedBySelf", "notcontrolling");
                         coi.doReload();
                     }
                 },