嗨，我正在尝试使用此代码发送带有xmlhttprequest的文件。

<script>
    var url= "http://localhost:80/....";
    $(document).ready(function(){
        document.getElementById('upload').addEventListener('change', function(e) {
            var file = this.files[0];
            var xhr = new XMLHttpRequest();
            xhr.file = file; // not necessary if you create scopes like this
            xhr.addEventListener('progress', function(e) {
                var done = e.position || e.loaded, total = e.totalSize || e.total;
                console.log('xhr progress: ' + (Math.floor(done/total*1000)/10) + '%');
            }, false);
            if ( xhr.upload ) {
                xhr.upload.onprogress = function(e) {
                    var done = e.position || e.loaded, total = e.totalSize || e.total;
                    console.log('xhr.upload progress: ' + done + ' / ' + total + ' = ' + (Math.floor(done/total*1000)/10) + '%');
                };
            }
            xhr.onreadystatechange = function(e) {
                if ( 4 == this.readyState ) {
                    console.log(['xhr upload complete', e]);
                }
            };
            xhr.open('post', url, true);
            xhr.setRequestHeader("Content-Type","multipart/form-data");
            xhr.send(file);
        }, false);
    });
</script>

但我收到此错误：请求被拒绝，因为未找到多部分边界，请帮助我。