stream: only check options once in Duplex ctor

This commit updates the Duplex constructor adding an if statement checking if options is undefined, and removes the check from the following three if statements. PR-URL: #20353 Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Anna Henningsen <anna@addaleax.net> Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

Author: danbev

lib/_stream_duplex.js

@@ -50,17 +50,19 @@ function Duplex(options) {
 
  Readable.call(this, options);
  Writable.call(this, options);
+ this.allowHalfOpen = true;
 
- if (options && options.readable === false)
- this.readable = false;
+ if (options) {
+ if (options.readable === false)
+ this.readable = false;
 
- if (options && options.writable === false)
- this.writable = false;
+  if (options.writable === false)
+  this.writable = false;
 
- this.allowHalfOpen = true;
- if (options && options.allowHalfOpen === false) {
- this.allowHalfOpen = false;
- this.once('end', onend);
+  if (options.allowHalfOpen === false) {
+  this.allowHalfOpen = false;
+  this.once('end', onend);
+ }
  }
 }