Question

function Person(){
    this.scream = function(){
        alert('NO NO NO!!!!');
    };
}

var steve = new Person();
steve.scream() // NO NO NO!!!!
Person.prototype.scream = function(){
    alert('YES YES YES!!!!');
}
steve.scream() // still NO NO NO!!!!

Is there a way to override ‘scream‘ without referencing steve explicitly? Think about the cases when you have may instances of Person.

Answer 1

No,

Having that Person declaration, every time you create a new “instance” of it the “constructor” will run and you’ll create a completely new scream function (closure) which you don’t have any reference to, except from the newly created object, steve.scream that is.

As an alternative you may do it like this:

function Person(){}

Person.prototype.scream = function(){
    alert('NO NO NO!!!!');
}

var steve = new Person();
steve.scream() // NO NO NO!!!!
Person.prototype.scream = function(){
    alert('YES YES YES!!!!');
}
steve.scream() // this time is YES YES YES!!!!

In which case the initial scream “method” is available only in one place, on the prototype, and you can overwrite it for all “instances”.