如何将文件追加到FormData（）？

Question

fd.append("upload", file)产生，

------WebKitFormBoundaryJnjpATRkxe2Duwwu
Content-Disposition: form-data; name="userid"

8022171621665209152
------WebKitFormBoundaryJnjpATRkxe2Duwwu
Content-Disposition: form-data; name="upload"; filename="sample.csv"
Content-Type: text/csv


------WebKitFormBoundaryJnjpATRkxe2Duwwu--

fd.append("upload", evt.target.result)产生，

------WebKitFormBoundaryITfVxS7FbNWfk3Ty
Content-Disposition: form-data; name="userid"

8022171621665209152
------WebKitFormBoundaryITfVxS7FbNWfk3Ty
Content-Disposition: form-data; name="upload"

"Healthy1.jpg","1","3","1","5"
"Unhealthy1.jpg","0","2","1","2"
"Water1.jpg","2","2","1","3"
------WebKitFormBoundaryITfVxS7FbNWfk3Ty--

但是我需要这个

------WebKitFormBoundaryITfVxS7FbNWfk3Ty
Content-Disposition: form-data; name="userid"

8022171621665209152
------WebKitFormBoundaryITfVxS7FbNWfk3Ty
Content-Disposition: form-data; name="upload"; filename="sample.csv"
Content-Type: text/csv

"Healthy1.jpg","1","3","1","5"
"Unhealthy1.jpg","0","2","1","2"
"Water1.jpg","2","2","1","3"
------WebKitFormBoundaryITfVxS7FbNWfk3Ty--

这是我的代码：

app.ports.uploadFile.subscribe(function(userid){
    var file = document.getElementById("csv").files[0];
    var fr = new FileReader();
    fr.readAsText(file, "UTF-8");
    fr.onload = function (evt) {
        console.log(evt.target.result);
        var fd = new FormData();
        fd.append("userid", userid)
        fd.append("upload", file) // <<<<< WHAT DO I PUT HERE?
        var xhr = new XMLHttpRequest()
        xhr.open('post', "http://localhost:8668/upload/ugimgset", true)
        xhr.setRequestHeader("Content-Type", "multipart/form-data")
        xhr.setRequestHeader("Authorization", "Bearer " + token() )
        xhr.send(fd)
    }
})

Answer 1

我发现了错误的根源

1. 我只需要FormData() -它会处理文件和隐藏字段。
2. 我正在覆盖Content-Type 。 当我这样做时，表单边界丢失了：

xhr.setRequestHeader（“ Content-Type”，“ multipart / form-data”）

更正后的代码如下（以及某些上下文）：

app.ports.uploadFile.subscribe(function(pathAndId){
    var [tasksrvPath, formId] = pathAndId
    try {
        var fd = new FormData(document.getElementById(formId));
        var r = new XMLHttpRequest()
        r.open("POST", tasksrvPath, true)
        r.setRequestHeader("Authorization", "Bearer " + token() )
        r.send(fd)
        r.onload = function() {
            app.ports.status.send(r.statusText)
        }
    } catch(e) {
        console.log(e.message);
    }
})