Use duck-typing as well as instanceof in sys.inspect

This makes it so that inspecting objects from other contexts works as expected.

lib/sys.js

@@ -65,7 +65,7 @@ exports.inspect = function (obj, showHidden, depth) {
 
     // Functions without properties can be shortcutted.
     if (typeof value === 'function' && keys.length === 0) {
-      if (value instanceof RegExp) {
+      if (isRegExp(value)) {
         return '' + value;
       } else {
         return '[Function]';
@@ -73,13 +73,13 @@ exports.inspect = function (obj, showHidden, depth) {
     }
 
     // Dates without properties can be shortcutted
-    if (value instanceof Date && keys.length === 0) {
+    if (isDate(value) && keys.length === 0) {
         return value.toUTCString();
     }
 
     var base, type, braces;
     // Determine the object type
-    if (value instanceof Array) {
+    if (isArray(value)) {
       type = 'Array';
       braces = ["[", "]"];
     } else {
@@ -89,13 +89,13 @@ exports.inspect = function (obj, showHidden, depth) {
 
     // Make functions say that they are functions
     if (typeof value === 'function') {
-      base = (value instanceof RegExp) ? ' ' + value : ' [Function]';
+      base = (isRegExp(value)) ? ' ' + value : ' [Function]';
     } else {
       base = "";
     }
 
     // Make dates with properties first say the date
-    if (value instanceof Date) {
+    if (isDate(value)) {
       base = ' ' + value.toUTCString();
     }
 
@@ -106,7 +106,7 @@ exports.inspect = function (obj, showHidden, depth) {
     }
 
     if (recurseTimes < 0) {
-      if (value instanceof RegExp) {
+      if (isRegExp(value)) {
         return '' + value;
       } else {
         return "[Object]";
@@ -140,7 +140,7 @@ exports.inspect = function (obj, showHidden, depth) {
             str = format(value[key], recurseTimes - 1);
           }
           if (str.indexOf('\n') > -1) {
-            if (value instanceof Array) {
+            if (isArray(value)) {
               str = str.split('\n').map(function(line) {
                 return '  ' + line;
               }).join('\n').substr(2);
@@ -191,6 +191,29 @@ exports.inspect = function (obj, showHidden, depth) {
   }
   return format(obj, (typeof depth === 'undefined' ? 2 : depth));
 };
+function isArray (ar) {
+  return ar instanceof Array
+      || Array.isArray(ar)
+      || (ar && ar !== Object.prototype && isArray(ar.__proto__));
+}
+function isRegExp (re) {
+  var s = ""+re;
+  return re instanceof RegExp // easy case
+      || typeof(re) === "function" // duck-type for context-switching evalcx case
+      && re.constructor.name === "RegExp"
+      && re.compile
+      && re.test
+      && re.exec
+      && s.charAt(0) === "/"
+      && s.substr(-1) === "/";
+}
+function isDate (d) {
+  if (d instanceof Date) return true;
+  if (typeof d !== "object") return false;
+  var properties = Date.prototype && Object.getOwnPropertyNames(Date.prototype);
+  var proto = d.__proto__ && Object.getOwnPropertyNames(d.__proto__);
+  return JSON.stringify(proto) === JSON.stringify(properties);
+}
 
 var pWarning;