我可以在javascript中获取原型的所有实例吗？

Question

It is easy to get the prototype of an object, but is there any way to get all the instances that has a specific prototype?

Something like this:

var allAnimals = Animal.prototype.getInstances();

One could write custom code to keep track of instantiated objects, but I'm interested in whether there is any build-in method for this.

Answer 1

you can get instances that have created on window like this

var o = [];
(for i in window)
{
    if(window[i] instanceof Animal) o.push(window[i]);
}

but this code, doesn't get instances which have not been created on window... you can create a method on Animal to create instance from that, and save it in a collection:

 +function () {

        var AnimalInstances = [];
        Animal = function (flag) {

            if (!flag) throw new Error("Invalid Instantiation");
        };
        Animal.Create = function () {

            var o = new Animal(true);
            AnimalInstances.push(o);
            return o;
        };
        Animal.GetInstances = function () {

            return AnimalInstances;
        };
    }();

or :

+function () {

        var AnimalInstances = [];
        Animal = function () {

            AnimalInstances.push(this);
        }
        Animal.GetInstances = function () {

            return AnimalInstances;
        };
    }();

Answer 2

You can try something like this

function A(f){
    this.field = f;
    A.instances.push(this);
}

A.instances = [];

so after

var one = new A(10), two=new A('123');

in A.instances will contain two created objects