gistfile1.pl

protoclass A {
    has $.x;
    
    submethod BUILD {
        $.x = 1;
    }
}
A.^prototype('foo', method {
    return 'A::foo';
});

protoclass B is A.new {
    submethod BUILD {
        $.x = 2;
    }
}

B.^prototype('foo', method {
    say self.A.foo;
    return 'B::foo';
});

B.^prototype('bar', method {
   return 'B::bar';
});

protoclass C is A.new { 
    submethod BUILD {
        $.x = 3;
    }
}

C.^prototype('baz', method {
    return 'C::baz';
});

protoclass D is B.new is C.new {
    submethod BUILD {
        $.x = 4;
    }
}

my $d = D.new;
say $d.baz; #=> "C.baz"
say $d.bar; #=> "A.foo\nB.bar"
say $d.foo; #=> "B.foo"

gistfile2.js

function A() {
    this.x = 1;
}
 
A.prototype.foo = function () {
    return 'A.foo';
}

B.prototype = new A;
B.prototype.constructor = B;
function B() { // New special constructor for B
    this.x = 3;
}

B.prototype.foo = function() { // overrides A.foo
    return "B.foo";
}

B.prototype.bar = function() {
    console.log(A.prototype.foo.call(this)); // super like function call
    return 'B.bar';
}

C.prototype = new A;
C.prototype.constructor = C; 
function C() {
    this.x = 4;
}

C.prototype.baz = function() {
    return 'C.baz';
}

var mult = new B;
mult = merge(new C, mult);
D.prototype = mult; // multi-inheritence
D.prototype.constructor = D;
function D() {
    this.x = 5;
}

var d = new D;
console.log(d.baz());
console.log(d.bar());
console.log(d.foo());