Calling base class function - class inheritance in JavaScript

Please check out the following example:

MyBaseClass = function(a) {
     this.a = a;
};

$.extend(MyBaseClass.prototype, {
    init: function() {
        console.log('I am initializing the base class');
    }
});

MyChildClass = $.extend(MyBaseClass, {
    init: function() {
        MyBaseClass.prototype.init();
        console.log('I am initializing the child class');
    }
});

var = new MyChildClass();
var.init();

Тhis should output both 'I am initializing the base class' and 'I am initializing the child class'.

I need to be able to inherit the class MyBaseClass, but still to be able to call his init() method at the beginning of the new init() method.

How do I do that?