Merge branch 'master' into add-getIn

README.md

@@ -48,7 +48,7 @@ not actually be immutable!
 
 ## Add-ons
 
-seamless-immutable is tightly focused on the mechanics of turning existing JavaScript data structurs into immutable variants.
+seamless-immutable is tightly focused on the mechanics of turning existing JavaScript data structures into immutable variants.
 Additional packages are available to build on this capability and enable additional programming models:
 
 |Library|Description|
@@ -184,6 +184,20 @@ mutableArray // ["hello", "world", "!!!"]
 
 Returns a mutable copy of the array. For a deeply mutable copy, in which any instances of `Immutable` contained in nested data structures within the array have been converted back to mutable data structures, call `Immutable.asMutable(obj, {deep: true})` instead.
 
+### isImmutable
+```javascript
+var array = Immutable(["hello", "world"]);
+var mutableArray = ["hello", "world"];
+
+Immutable.isImmutable(array)
+// returns true
+
+Immutable.isImmutable(mutableArray)
+// returns false
+```
+
+Returns whether an object is immutable or not.
+
 ## Immutable Object
 
 Like a regular Object, but immutable! You can construct these by passing an

seamless-immutable.development.js

@@ -99,13 +99,12 @@ function immutableInit(config) {
   ]);
 
   function ImmutableError(message) {
-    var err       = new Error(message);
-    // TODO: Consider `Object.setPrototypeOf(err, ImmutableError);`
-    err.__proto__ = ImmutableError;
-
-    return err;
+    this.name = 'MyError';
+    this.message = message;
+    this.stack = (new Error()).stack;
   }
-  ImmutableError.prototype = Error.prototype;
+  ImmutableError.prototype = new Error;
+  ImmutableError.prototype.constructor = Error;
 
   function makeImmutable(obj, bannedMethods) {
     // Tag it so we can quickly tell it's immutable later.