What is the easiest way to test for class membership in coffeescript?

Question

I\'m looking for an equivalent of Ruby\'s \"blah\".is_a?(String) of Objective-C\'s [@\"blah\" isKindOfClass:[NSString class]]

Answer 1

Do you want to test whether an object is descended from a particular class? Then you want the instanceof keyword. (It's not something added by CoffeeScript; it's a part of JavaScript.) CoffeeScript classes are set up so that if you write

class A
class B extends A
class C extends B

then the following is true:

(new A) instanceof A
(new B) instanceof B and (new B) instanceof A
(new C) instanceof C and (new C) instanceof B and (new C) instanceof A

Also, any object will return true for instanceof Object.

If you want to test the specific class that an object is an instance of, use .constructor. For instance,

(new B).constructor is B

or if you'd like to use a string,

(new B).constructor.name is 'B'