Enables cross-origin Web Workers (#35483)

app/javascript/mastodon/utils/workers.ts

@@ -0,0 +1,29 @@
+/**
+ * Loads Web Worker that is compatible with cross-origin scripts for CDNs.
+ *
+ * Returns null if the environment doesn't support web workers.
+ */
+export function loadWorker(url: string | URL, options: WorkerOptions = {}) {
+  if (!('Worker' in window)) {
+    return null;
+  }
+
+  try {
+    // Check if the script origin and the window origin are the same.
+    const scriptUrl = new URL(import.meta.url);
+    if (location.origin === scriptUrl.origin) {
+      // Not cross-origin, can just load normally.
+      return new Worker(url, options);
+    }
+  } catch (err) {
+    // In case the URL parsing fails.
+    console.warn('Error instantiating Worker:', err);
+  }
+
+  // Import the worker script from a same-origin Blob.
+  const contents = `import ${JSON.stringify(url)};`;
+  const blob = URL.createObjectURL(
+    new Blob([contents], { type: 'text/javascript' }),
+  );
+  return new Worker(blob, options);
+}