react.js

function appUI(actions) {
    return React.createClass({
        render: function () {
            return React.DOM.h1({onClick: actions.doit}, 'LOL');
        }
    });
}

var data = {}

function render() {
    React.render(App(data), elem);
}

var App = AppUI({
    login: function () {
        data.user = {name: 'Bob'};
    }
});

render();