/**
 * Emulate detection of required form fields in browsers which do not support the `required` attribute
 *
 * Borrowed from http://www.html5rocks.com/en/tutorials/forms/constraintvalidation/#toc-safari
 */
emulateRequiredFormFields: function () {
    var is_chrome = navigator.userAgent.indexOf('Chrome') > -1,
        is_chrome_ios = navigator.userAgent.match('CriOS'),
        is_explorer = navigator.userAgent.indexOf('MSIE') > -1,
        is_firefox = navigator.userAgent.indexOf('Firefox') > -1,
        is_safari = navigator.userAgent.indexOf('Safari') > -1,
        is_opera = navigator.userAgent.toLowerCase().indexOf('op') > -1,
        is_ios = /iPad|iPhone|iPod/.test(navigator.userAgent) && !window.MSStream;

    if (is_chrome && is_safari) {
        is_safari = false;
    }

    if (is_chrome && is_opera) {
        is_chrome = false;
    }

    // Only applies to Safari (desktop and mobile) or Chrome on iOS
    if (is_safari || is_ios || is_chrome_ios) {
        var forms = document.getElementsByTagName('form');

        for (var i = 0; i < forms.length; i++) {
            forms[i].noValidate = true;

            forms[i].addEventListener('submit', function (event) {
                // Prevent submission if checkValidity on the form returns false.
                if (!event.target.checkValidity()) {
                    event.preventDefault();
                    alert('You are missing required fields to submit this form.');
                }
            }, false);
        }
    }
},