optimize utf8Decode (#3085)

lib/web/websocket/util.js

@@ -209,24 +209,21 @@ const fatalDecoder = hasIntl ? new TextDecoder('utf-8', { fatal: true }) : undef
  * Converts a Buffer to utf-8, even on platforms without icu.
  * @param {Buffer} buffer
  */
-function utf8Decode (buffer) {
-  if (hasIntl) {
-    return fatalDecoder.decode(buffer)
-  } else {
-    if (!isUtf8?.(buffer)) {
-      // TODO: remove once node 18 or < node v18.14.0 is dropped
-      if (!isUtf8) {
+const utf8Decode = hasIntl
+  ? fatalDecoder.decode.bind(fatalDecoder)
+  : !isUtf8
+      ? function () { // TODO: remove once node 18 or < node v18.14.0 is dropped
         process.emitWarning('ICU is not supported and no fallback exists. Please upgrade to at least Node v18.14.0.', {
           code: 'UNDICI-WS-NO-ICU'
         })
+        throw new TypeError('Invalid utf-8 received.')
+      }
+      : function (buffer) {
+        if (isUtf8(buffer)) {
+          return buffer.toString('utf-8')
+        }
+        throw new TypeError('Invalid utf-8 received.')
       }
-
-      throw new TypeError('Invalid utf-8 received.')
-    }
-
-    return buffer.toString('utf-8')
-  }
-}
 
 module.exports = {
   isConnecting,