使用js sdk进行多文件上传报错

我根据阿里云js sdk的demo做了一个上传功能，使用原生的file input多文件上传，第一个文件上传成功，到第二个文件上传的时候报错：
Error: The specified upload does not exist. The upload ID may be invalid, or the upload may have been aborted or completed.
    at o.<anonymous> (http://gosspublic.alicdn.com/aliyun-oss-sdk-4.10.1.min.js:4:18257)
    at n (http://gosspublic.alicdn.com/aliyun-oss-sdk-4.10.1.min.js:12:806)
    at Generator._invoke (http://gosspublic.alicdn.com/aliyun-oss-sdk-4.10.1.min.js:12:1851)
    at Generator.e.(anonymous function) [as next] (http://gosspublic.alicdn.com/aliyun-oss-sdk-4.10.1.min.js:12:985)
    at n (http://gosspublic.alicdn.com/aliyun-oss-sdk-4.10.1.min.js:12:806)
    at l (http://gosspublic.alicdn.com/aliyun-oss-sdk-4.10.1.min.js:12:2283)
    at Generator._invoke (http://gosspublic.alicdn.com/aliyun-oss-sdk-4.10.1.min.js:12:1628)
    at Generator.e.(anonymous function) [as next] (http://gosspublic.alicdn.com/aliyun-oss-sdk-4.10.1.min.js:12:985)
    at a (http://gosspublic.alicdn.com/aliyun-oss-sdk-4.10.1.min.js:6:28350)
    at <anonymous>


我的js功能代码：
function uploadFile(client) {
    var file = document.getElementById('file').files[1];
    var key = folder + file.name;
    console.log(file.name + ' => ' + key);
    return client.multipartUpload(key, file, {
        checkpoint: checkpoint,
        progress: progressFunc
    }).catch(function (err) {
        console.log(err);
    }).then(function (res) {
        console.log('upload success: %j', res);
    });
}


请问有没有人知道怎么在js sdk重置这个upload id?