feat: add Node.js <= 18 deprecation warning

- Add deprecation warning for Node.js versions 18 and below
- Extract shouldShowDeprecationWarning function with robust version parsing
- Parse major version number from process.version using regex
- Handle edge cases: null version, malformed strings, browser environments
- Display informative warning message directing users to upgrade to Node.js 20+
- Include link to GitHub discussion for more information

Author: grdsdev

src/index.ts

@@ -40,15 +40,29 @@ export const createClient = <
   return new SupabaseClient<Database, SchemaName, Schema>(supabaseUrl, supabaseKey, options)
 }
 
-// Check for Node.js 18 deprecation
-if (
-  typeof window === 'undefined' &&
-  typeof process !== 'undefined' &&
-  process.version &&
-  process.version.startsWith('v18')
-) {
+// 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 is deprecated and will no longer be supported in future versions of @supabase/supabase-js. ` +
+    `⚠️  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`
   )