How to use polymorphism in Javascript
<p>Most languages use single inheritance for classes. And it's fairly obvious the pattern to do this (for example in Swift code below).  I am still trying to wrap my head around the pattern in JavaScript to create a object hierarchy and re-use class functions and override class functions</p>

<pre><code>class animal {
    func talk() {
        print ("?")
    }
}

class bird : animal {
    override func talk() {
        print("tweet tweet")
    }
    func fly() {
        print("flap flap")
    }
}

class parrot : bird {
    override func talk() {
        print("polly want a cracker")
    }
}

var a = animal()
var b = bird()
var p = parrot()

a.talk()  /// ?
b.talk()  /// tweet tweet
b.fly()   /// flap flap
p.talk()  /// polly want a cracker
p.fly()   /// flap flap
</code></pre>

<p>I think my problem is the Javascript code looks nothing like this. What is the equivalent Javascript code so I can figure out the pattern?</p>