some random optimizations

Hopefully…

debug.js

@@ -83,7 +83,10 @@ function debug(namespace) {
     if (null == self.useColors) self.useColors = exports.useColors();
     if (null == self.color && self.useColors) self.color = selectColor();
 
-    var args = Array.prototype.slice.call(arguments);
+    var args = new Array(arguments.length);
+    for (var i = 0; i < args.length; i++) {
+      args[i] = arguments[i];
+    }
 
     args[0] = exports.coerce(args[0]);
 
@@ -110,9 +113,9 @@ function debug(namespace) {
       return match;
     });
 
-    if ('function' === typeof exports.formatArgs) {
-      args = exports.formatArgs.apply(self, args);
-    }
+    // apply env-specific formatting
+    args = exports.formatArgs.apply(self, args);
+
     var logFn = enabled.log || exports.log || console.log.bind(console);
     logFn.apply(self, args);
   }

node.js

@@ -80,12 +80,12 @@ exports.formatters.o = exports.formatters.O = function(v) {
  */
 
 function formatArgs() {
-  var args = [];
   var len = arguments.length;
+  var args = new Array(len);
   var useColors = this.useColors;
   var name = this.namespace;
   for (var i = 0; i < len; i++) {
-    args.push(arguments[i]);
+    args[i] = arguments[i];
   }
 
   if (useColors) {