path: join refactor

Author: Mnwa

lib/path.js

@@ -368,20 +368,19 @@ const win32 = {
     if (args.length === 0)
       return '.';
 
-    let joined;
-    let firstPart;
-    for (let i = 0; i < args.length; ++i) {
-      const arg = args[i];
+    let joined = null;
+    let firstPart = null;
+    for (const arg of args) {
       validateString(arg, 'path');
       if (arg.length > 0) {
-        if (joined === undefined)
+        if (joined === null)
           joined = firstPart = arg;
         else
           joined += `\\${arg}`;
       }
     }
 
-    if (joined === undefined)
+    if (joined === null)
       return '.';
 
     // Make sure that the joined path doesn't start with two slashes, because