限制上传文件大小和格式的jQuery插件实例

                if ($.inArray(extension, options.allowedExtensions) == -1) {
                    options.extensionerror();
                    $(this).focus();
                } else {
                    try {
                        var size = 0;
                        if ($.browser.msie) {//ie旧版浏览器
                            var fileMgr = new ActiveXObject(“Scripting.FileSystemObject”);
                            var fileObj = fileMgr.getFile(filePath);
                            size = fileObj.size; //byte
                            size = size / 1024;//kb
                            //size = size / 1024;//mb
                        } else {//其它浏览器
                            size = $(this)[0].files[0].size;//byte
                            size = size / 1024;//kb
                            //size = size / 1024;//mb
                        }
                        if (size > options.maxSize) {