How to access blob metadata using the Azure JavaScript SDK? - azure

Question

How do I read metadata for a blob in azure via the JavaScript SDK?
When I iterate the blobs returned from the specified container I see a metadata property:
But it's undefined, even though there is definitely metadata associated with the blob:
Is there something else I need to do to get the metadata to populate?
import { BlobServiceClient, SharedKeyCredential } from "#azure/storage-blob";
const account = "<redacted>";
const accountKey = "<redacted>";
const sharedKeyCredential = new SharedKeyCredential(account, accountKey);
const blobServiceClient = new BlobServiceClient(`https://${account}.blob.core.windows.net`, sharedKeyCredential);
const containerClient = blobServiceClient.getContainerClient(podcastName);
const blobs = await containerClient.listBlobsFlat({ include: ["metadata"] });
for await (const blob of blobs) {
console.log(blob.name);
//blob.metadata is undefined
}
// package.json relevant dependencies
"dependencies": {
"#azure/storage-blob": "^12.0.0-preview.2
}

Answer 1

// You can try this:
for await (const blob of containerClient.listBlobsFlat()) {
const blockBlobClient = containerClient.getBlockBlobClient(blob.name);
const meta = (await blockBlobClient.getProperties()).metadata;
console.log(meta);
// process metadata
}
I am assuming you have already declared blockBlobClient and containerClient.
If you haven't already declared blockBlobClient and containerClient ,then you can refer here

Answer 2

I test it's null, then I use getProperties() to get the metadata and it worked, you could have a try.
const containerName = "test";
const blobName = "test.txt";
let response;
let marker;
do {
response = await containerURL.listBlobFlatSegment(aborter);
marker = response.marker;
for(let blob of response.segment.blobItems) {
const url= BlockBlobURL.fromContainerURL(containerURL,blob.name);
const pro=await url.getProperties(aborter);
console.log(pro.metadata);
}
} while (marker);

Answer 3

You can fetch the properties for a blob with the getBlobMetadata method.
var storage = require('azure-storage');
var blobService = storage.createBlobService();
var containerName = 'your-container-name';
var blobName = 'my-awesome-blob';
blobService.getBlobMetadata(containerName, blobName, function(err, result, response) {
if (err) {
console.error("Couldn't fetch metadata for blob %s", blobName);
console.error(err);
} else if (!response.isSuccessful) {
console.error("Blob %s wasn't found container %s", blobName, containerName);
} else {
console.log("Successfully fetched metadata for blob %s", blobName);
console.log(result.metadata);
}
});
For more details, you could refer to this article.

Answer 4

in v12 you can retrieve metadata when listing blobs by passing the option includeMetadata: true
await containerClient.listBlobsFlat({ includeMetadata: true });
https://github.com/Azure/azure-sdk-for-js/blob/d2730549e078571df008e929f19c07aaf8f9efd9/sdk/storage/storage-blob/test/containerclient.spec.ts#L198