getBoundingClientRect not working about triflejs HOT 5 CLOSED

    var page = require('webpage').create(),
        system = require('system'),
        address, output, size;

    var output = "test.png";
    var address ="http://embed.plnkr.co/RxznuEsxVabaRVTGMbKa/preview";

    page.viewportSize = { width: 1800, height: 768 };
    page.open(address, function (status) {
        if (status !== 'success') {
            console.log('Unable to load the address!');
            phantom.exit();
        } else {
            window.setTimeout(function () {
                console.log(page.evaluate(function() {
                    var response;
                    var element = document.getElementById("test");    // script error, getBoundingClientRect not defined
                    //var element = document.querySelector('H1');         // returns {}
                    //var element = document.documentElement            // returns {}
                    var rect = element.getBoundingClientRect();
                    return rect;
                }));
                page.render(output);
                phantom.exit();
            }, 1000);
        }
    });

      document.getElementById("test")