Stick THIS in your browser and run it.

rxdd.js

        Rx.Observable.select = function (element, source) {
            return source.select(function (value) {
                return {
                    element: element,
                    value: value
                };
            });
        };

        Rx.Observable.prototype.append = function (type) {
            return this.selectMany(function (x) {
                var element = document.createElement(type);
                x.element.appendChild(element);
                return x.value
                    .finallyAction(function () {
                        x.element.removeChild(element);
                    })
                    .select(function (value) {
                        return {
                            element: element,
                            value: value
                        };
                    });
            });
        };

        Rx.Observable.prototype.text = function (func) {
            return this.doAction(function (x) {
                x.element.innerText = func(x.value);
            });
        };

        Rx.Observable.prototype.attr = function (name, func) {
            return this.doAction(function (x) {
                x.element.setAttribute(name, func(x.value));
            });
        };

        Rx.Observable.prototype.style = function (name, func) {
            return this.doAction(function (x) {
                var val = func(x.value);

                if (typeof val === 'number') { val = val + 'px'; }

                x.element.style[name] = val;
            });
        };

        // - Side Effects

        var source = Rx.Observable.timer(0, 100).select(function () {
            return Rx.Observable.timer(0, 250).take(10).merge(Rx.Observable.never()).select(function () {
                return Math.floor(Math.random() * 50);
            });
        });

        Rx.Observable.select(document.body, source)
            .append('span')
            .text(function (x) { return x; })
            .style('paddingBottom', function (x) { return x; })
            .style('borderBottomWidth', function (x) { return 50 - x + 1; })
            .subscribe();

style.css

    span {
        display: inline-block;
        margin: 0px;
        border: 5px solid black;
        transition: padding 0.1s, border 0.1s;
        width: 25px;
        text-align: center;
    }