/**
 * Returns active device detected by Bootstrap
 *
 * @author Petr Knap <dev@petrknap.cz>
 *
 * @param {String} [testerId="getBootstrapDevice"] Identifier used for prepended div element
 * @param {String} [defaultDevice="lg"] Default device
 *
 * @returns {String} Active device (xs|sm|md|lg)
 */
function getBootstrapDevice(testerId, defaultDevice) {
    var $body, $tester;

    if(!testerId) {
        testerId = "getBootstrapDevice";
    }

    if(!defaultDevice) {
        defaultDevice = "lg";
    }

    $body = $("body");
    $tester = $body.find("#" + testerId);

    if($tester.length == 0) { // Insert tester
        $body.prepend('' +
        '<div id="' + testerId + '" style="position: absolute; z-index: -999">' +
        '   <div class="visible-xs-block">&nbsp;</div>' +
        '   <div class="visible-sm-block">&nbsp;</div>' +
        '   <div class="visible-md-block">&nbsp;</div>' +
        '   <div class="visible-lg-block">&nbsp;</div>' +
        '</div>' +
        '');
        return getBootstrapDevice(testerId, defaultDevice);
    }
    else {
        $tester.find("div").each(function() {
            if($(this).css("display") == "block") {
                defaultDevice = $(this).attr('class').split("-")[1];
                return false; // Break the loop
            }
        });
        return defaultDevice;
    }
}