从 WebAPI 收到的空响应标头

Question

我在前面使用 ASP.NET WebApi 和 ReactJs 应用程序，我正在创建一个 Get 方法来从服务器下载文件，并且我尝试在响应标头中设置 Content-Type 和 Content-Length：

        var result = new HttpResponseMessage(HttpStatusCode.OK);
        result.Content = new StreamContent(new MemoryStream(bytes));
        result.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
        result.Content.Headers.ContentLength = bytes.Length;

当我使用如下 fetch 方法从 ReactJs 应用程序调用此方法时：

    await fetch(`someservice/${clientid}/download/${fileName}`, { responseType: "arraybuffer" })
    .then((response) => {
        const reader = response.body.getReader();

        //get total length
        const contentLength = response.headers.get('Content-Length');
        console.log(response.headers);

        //read the data
        let receivedLength = 0; // received that many bytes at the moment
        let chunks = []; // array of received binary chunks (comprises the body)
        while (true) {
            const { done, value } = reader.read();

            if (done) {
                break;
            }
            console.log(value);
            chunks.push(value);
            receivedLength += value.length;

            console.log(`Received ${receivedLength} of ${contentLength}`)
        }

        //concatenate chunks into single Uint8Array
        let chunksAll = new Uint8Array(receivedLength);
        let position = 0;
        for (let chunk of chunks) {
            chunksAll.set(chunk, position);
            position += chunk.length;
        }
    });

我收到了没有 Content-Type 和 Content-Length 标头的响应：

但是 Content-Type 和 Content-Length 不是有效的标头吗？

Answer 1

fetch api JavaScript 中的响应标头已实现为迭代器，而不是 object，您可以尝试在下面访问标头：-

  for (var header of respone.headers.entries()) {
                    console.log(header);
                } 

循环中的每个 header 项目将是一个字符串数组，其中第一个元素是键，第二个元素是值。