Simple JS for building a DOM tag containing the Pinterest data from the URL and loading the external Pinterest script to parse it.

gistfile1.js

YUI.add("muse-pin-it-button", function (Y) {
    var isInit = false;
    var putButtonMarkupOnPage = function () {
        var urlParams = window.location.search.substr(1) + "";
        var params = Y.QueryString.parse(urlParams);
        var url = params.url;
        var description = params.description;
        var media = params.media;
        Y.one('body').setContent('<a data-pin-config="beside" href="//pinterest.com/pin/create/button/?url=' + url + '&media=' + media + '&description=' + description + '" data-pin-do="buttonPin" ><img src="//assets.pinterest.com/images/pidgets/pin_it_button.png" /></a>');
    }
    var loadExternalPinterestScriptToParsePage = function () {
        Y.use('pinterestPinit', function (Y1) {
            Y.log("Pinterest Script Loaded");
        });
    }
    Y.PinItButton = {
        init: function () {
            if (isInit) {
                return;
            }
            isInit = true;
            Y.log("Y.PinItButton.init();");
            putButtonMarkupOnPage();
            loadExternalPinterestScriptToParsePage();
        }
    }
}, "0.1", {
    requires: ["node", "querystring-parse"]
});