frontend.recaptcha.js

(function recaptcha(){
    var $forms = $('form.recaptcha-enabled');
    if (!$forms.length) return;

    var tokenUpdater = new RecaptchaTokenUpdater(cdata.RECAPTCHA_SITE_KEY);

    $forms.each(function(){
        var $form = $(this),
            $input = $('<input type="hidden" name="g-recaptcha-response">').appendTo($form);

        tokenUpdater.onUpdate(function(token){
            $input.val(token);
        });
        $form.one('input change', tokenUpdater.start);
        $form.on('submit', function(e){
            if (tokenUpdater.hasToken()) return;

            e.preventDefault();
            $form.find('[type=submit]').prop('disabled', true);

            tokenUpdater.onUpdate(function(){
                e.target.submit();
            });
            tokenUpdater.start();
        })
    });

    function RecaptchaTokenUpdater(siteKey) {
        $.getScript('https://www.google.com/recaptcha/api.js?render=' + siteKey);
        var token;
        var callbacks = [function(t){ token = t; }];
        this.onUpdate = function(fn) {
            callbacks.push(fn);
        };
        this.hasToken = function(){ return !!token; };
        this.start = function once(){
            if (once.started) return;
            once.started = true;
            (function init(){
                if (!window.grecaptcha) return setTimeout(init, 10);
                grecaptcha.ready(function(){
                    update();
                    setInterval(update, 30 * 1000);
                });
            })();
        };
        function update() {
            grecaptcha.execute(siteKey).then(function(token){
                $.each(callbacks, function (cb) { cb(token); });
            });
        }
    }
})();