Function _addEvent

client/vendors/mousetrap.js:215–222

* cross browser add event method * * @param {Element|HTMLDocument} object * @param {string} type * @param {Function} callback * @returns void

(object, type, callback)

     * @returns void
     */
    function _addEvent(object, type, callback) {
        if (object.addEventListener) {
            object.addEventListener(type, callback, false);
            return;
        }

        object.attachEvent('on' + type, callback);
    }

    /**
     * takes the event and returns the key character