path: refactor path joining logic for clarity and performance

PR-URL: #59781
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Minwoo Jung <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>

Author: wlgh1553

lib/path.js

@@ -24,6 +24,7 @@
 const {
   ArrayPrototypeIncludes,
   ArrayPrototypeJoin,
+  ArrayPrototypePush,
   ArrayPrototypeSlice,
   FunctionPrototypeBind,
   StringPrototypeCharCodeAt,
@@ -506,22 +507,21 @@ const win32 = {
     if (args.length === 0)
       return '.';
 
-    let joined;
-    let firstPart;
+    const path = [];
     for (let i = 0; i < args.length; ++i) {
       const arg = args[i];
       validateString(arg, 'path');
       if (arg.length > 0) {
-        if (joined === undefined)
-          joined = firstPart = arg;
-        else
-          joined += `\\${arg}`;
+        ArrayPrototypePush(path, arg);
       }
     }
 
-    if (joined === undefined)
+    if (path.length === 0)
       return '.';
 
+    const firstPart = path[0];
+    let joined = ArrayPrototypeJoin(path, '\\');
+
     // Make sure that the joined path doesn't start with two slashes, because
     // normalize() will mistake it for a UNC path then.
     //