I have written this code to fetch data and I am getting response like this

async function streamToString(readableStream) {
  return new Promise((resolve, reject) => {
    const chunks = [];
    readableStream.on("data", (data) => {
      chunks.push(data.toString());
    });
    readableStream.on("end", () => {
      resolve(chunks.join(""));
    });
    readableStream.on("error", reject);
  });
}

if (type == "download") {
  const name = req.query.name || req.body.name;
  const itemname = req.query.itemname || req.body.itemname;
  var container = name ? name : "securesharecc";
  const containerClient = await blobServiceClient.getContainerClient(container);
  const blobName = itemname ? itemname : "sample.png";
  const blockBlobClient = containerClient.getBlockBlobClient(blobName);
  const downloadBlockBlobResponse = await blockBlobClient.download(0);
  console.log("\nDownloaded blob content...");
  var base64string = await streamToString(downloadBlockBlobResponse.readableStreamBody);
  console.log("\t", base64string);
  context.res = {
    body: { data: base64string }
  };
  context.done();
}

so this code shows a string of a file using the item name in a container from azure.

But I'm getting responses like this

{
  "data": "PNG\r\n\u001a\n\u0000\u0000\u0000\rIHDR\u0000\u0000\u0002�\u0000\u0000\u0001�\b\u0002\u0000\u0000\u0000\u000f�\u001fl\u0000\u0000\u0000\u0001sRGB\u0000��\u001c�\u0000\u0000\u0000\u0004gAMA\u0000\u0000��\u000b ....."
}

What to code if I want to directly download this file instead of showing contents, how to do this?

CodePudding user response：

Please try by changing your streamToString method to something like:

async function streamToString(readableStream) {
  return new Promise((resolve, reject) => {
    let chunks = Buffer.from([]);
    readableStream.on("data", (data) => {
      chunks = Buffer.concat([chunks, data], chunks.length   data.length);
    });
    readableStream.on("end", () => {
      resolve(chunks);
    });
    readableStream.on("error", reject);
  });
}

Essentially image files are binary files and you should not try to convert its data into string.