function dellogfile(beforedays) {
    var fso = new ActiveXObject("Scripting.FileSystemObject");
    var dir = fso.GetFolder("C:\\WINDOWS\\system32\\LogFiles");    //改成你的 IIS 日志目录
    for (var fc = new Enumerator(dir.SubFolders); !fc.atEnd(); fc.moveNext()) {
        if (fc.item().name.substr(0,5) == "W3SVC") {
            for (var logfiles = new Enumerator(fc.item().Files); !logfiles.atEnd(); logfiles.moveNext()) {
                var fileName = logfiles.item().name;
                var year = "20" + fileName.substr(2, 2);
                var mouth = fileName.substr(4, 2);
                var day = fileName.substr(6, 2);
                var days = Math.round(((new Date()).getTime() - Date.UTC(year, mouth - 1, day)) / 1000 / 60 / 60 / 24);
                if (days >= beforedays) logfiles.item().Delete();
            }
        }
    }
}

dellogfile(3);