net: prefer === to ==

* Change === to == in one place
* Add explanation about another non-strict if-statement

PR-URL: https://github.com/nodejs/node/pull/11513
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

lib/net.js

@@ -146,6 +146,9 @@ function Socket(options) {
   } else if (options.fd !== undefined) {
     this._handle = createHandle(options.fd);
     this._handle.open(options.fd);
+    // options.fd can be string (since it user-defined),
+    // so changing this to === would be semver-major
+    // See: https://github.com/nodejs/node/pull/11513
     if ((options.fd == 1 || options.fd == 2) &&
         (this._handle instanceof Pipe) &&
         process.platform === 'win32') {
@@ -1069,7 +1072,7 @@ function afterConnect(status, handle, req, readable, writable) {
   self.connecting = false;
   self._sockname = null;
 
-  if (status == 0) {
+  if (status === 0) {
     self.readable = readable;
     self.writable = writable;
     self._unrefTimer();