Function eventSupported

FlashViewer-HTML5 Video/flashViewer.user.js:308–341

(eventName, elem)

        // 事件支持检测.
        // 比如 eventSupported('fullscreenchange', document);
        function eventSupported(eventName, elem) {
            elem = elem || document.createElement('div');
            var prefix = ['o', 'ms', 'moz', 'webkit', ''];

            var l = prefix.length;
            var pEventName;
            var isFunction;
            var setAttr;

            while(l --) {
                pEventName = 'on' + prefix[l] + eventName;

                if (pEventName in elem) {
                    return pEventName.slice(2);
                } else if (typeof elem.setAttribute == 'function') { // setAttribute 是元素节点的方法
                    setAttr = false;
                    if (!elem.hasAttribute(pEventName)) {
                        setAttr = true;
                        elem.setAttribute(pEventName, 'return;');
                    };

                    isFunction = typeof elem[pEventName] == 'function';

                    if (setAttr) elem.removeAttribute(pEventName);

                    if (isFunction) {
                        return pEventName.slice(2);
                    };
                };
            };

            return false;

        };

        // 在指定对象上保存数据
        var data = (function () {