fix: add Node 18 deprecation notice

src/index.ts

@@ -39,3 +39,31 @@ export const createClient = <
 ): SupabaseClient<Database, SchemaName, Schema> => {
   return new SupabaseClient<Database, SchemaName, Schema>(supabaseUrl, supabaseKey, options)
 }
+
+// Check for Node.js <= 18 deprecation
+function shouldShowDeprecationWarning(): boolean {
+  if (
+    typeof window !== 'undefined' ||
+    typeof process === 'undefined' ||
+    process.version === undefined ||
+    process.version === null
+  ) {
+    return false
+  }
+
+  const versionMatch = process.version.match(/^v(\d+)\./)
+  if (!versionMatch) {
+    return false
+  }
+
+  const majorVersion = parseInt(versionMatch[1], 10)
+  return majorVersion <= 18
+}
+
+if (shouldShowDeprecationWarning()) {
+  console.warn(
+    `⚠️  Node.js 18 and below are deprecated and will no longer be supported in future versions of @supabase/supabase-js. ` +
+      `Please upgrade to Node.js 20 or later. ` +
+      `For more information, visit: https://github.com/orgs/supabase/discussions/37217`
+  )
+}