lib: use helper for readability

Used an extra `checkReusedHandle()` helper function to increase readability.

lib/internal/js_stream_socket.js

@@ -22,52 +22,39 @@ const kCurrentWriteRequest = Symbol('kCurrentWriteRequest');
 const kCurrentShutdownRequest = Symbol('kCurrentShutdownRequest');
 const kPendingShutdownRequest = Symbol('kPendingShutdownRequest');
 
-function isClosing() {
-  let socket = this[owner_symbol];
+function checkReusedHandle(t) {
+  let socket = t[owner_symbol];
 
-  if (socket.constructor.name === 'ReusedHandle') {
+  if (socket.constructor.name === 'ReusedHandle')
     socket = socket.handle;
-  }
+}
+
+function isClosing() {
+  checkReusedHandle(this);
 
   return socket.isClosing();
 }
 
 function onreadstart() {
-  let socket = this[owner_symbol];
-
-  if (socket.constructor.name === 'ReusedHandle') {
-    socket = socket.handle;
-  }
+  checkReusedHandle(this);
 
   return socket.readStart();
 }
 
 function onreadstop() {
-  let socket = this[owner_symbol];
-
-  if (socket.constructor.name === 'ReusedHandle') {
-    socket = socket.handle;
-  }
+  checkReusedHandle(this);
 
   return socket.readStop();
 }
 
 function onshutdown(req) {
-  let socket = this[owner_symbol];
-
-  if (socket.constructor.name === 'ReusedHandle') {
-    socket = socket.handle;
-  }
+  checkReusedHandle(this);
 
   return socket.doShutdown(req);
 }
 
 function onwrite(req, bufs) {
-  let socket = this[owner_symbol];
-
-  if (socket.constructor.name === 'ReusedHandle') {
-    socket = socket.handle;
-  }
+  checkReusedHandle(this);
 
   return socket.doWrite(req, bufs);
 }