observable collection

collection.js

'use strict';

const rx = require('rx');

let Collection = function () {
    this._data = [];
    this._onPush = undefined;
    this._observable = rx.Observable.create((observer) => {
        this._onPush = function () {
            observer.onNext(this._data);
        }
    });
    Object.defineProperty(this, 'data', {
        get: () => {
            return this._data;
        },
        set: (value) => {
            throw new Error('Prohibited to change readonly property');
        }
    });    
};

Collection.prototype.push = function(value) {
    this._data.push(value);
    this._onPush(value);
};

Collection.prototype.subscribe = function(cb) {
    this._observable.subscribe(cb);
};

let col = new Collection();

col.subscribe(ss => console.log(ss));

col.push(1);
col.push(2);
col.push(3);
col.push(4);
col.push(5);
col.push(6);

// console output:
// [ 1 ]
// [ 1, 2 ]
// [ 1, 2, 3 ]
// [ 1, 2, 3, 4 ]
// [ 1, 2, 3, 4, 5 ]
// [ 1, 2, 3, 4, 5, 6 ]