lib: scope loop variables

Refactor instances in `lib` where a loop variable is redeclared in the
same scope with `var`. In these cases, `let` can be used to scope the
variable declarations more precisely.

PR-URL: https://github.com/nodejs/node/pull/4965
Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/path.js

@@ -282,7 +282,7 @@ win32.relative = function(from, to) {
   }
 
   var outputParts = [];
-  for (var i = samePartsLength; i < lowerFromParts.length; i++) {
+  for (var j = samePartsLength; j < lowerFromParts.length; j++) {
     outputParts.push('..');
   }
 
@@ -503,7 +503,7 @@ posix.relative = function(from, to) {
   }
 
   var outputParts = [];
-  for (var i = samePartsLength; i < fromParts.length; i++) {
+  for (var j = samePartsLength; j < fromParts.length; j++) {
     outputParts.push('..');
   }
 

lib/util.js

@@ -13,8 +13,8 @@ const formatRegExp = /%[sdj%]/g;
 exports.format = function(f) {
   if (typeof f !== 'string') {
     var objects = [];
-    for (var i = 0; i < arguments.length; i++) {
+    for (var index = 0; index < arguments.length; index++) {
-      objects.push(inspect(arguments[i]));
+      objects.push(inspect(arguments[index]));
     }
     return objects.join(' ');
   }