AWS SDK for JavaScript v3

await s3.send(
  new PutObjectCommand({
    Bucket: bucket,
    Key: key,
    Body: body,
    ContentType: "text/plain",
  }),
);

// Handles multipart, concurrency and retries for you — use it for anything
// whose size you do not control.
const upload = new Upload({
  client: s3,
  params: { Bucket: bucket, Key: key, Body: body },
  queueSize: 4,
  partSize: 8 * 1024 * 1024,
});
upload.on("httpUploadProgress", (p) => console.log(`${p.loaded}/${p.total ?? "?"}`));
await upload.done();

const object = await s3.send(new GetObjectCommand({ Bucket: bucket, Key: key }));
const text = await object.Body.transformToString();

for await (const page of paginateListObjectsV2(
  { client: s3 },
  { Bucket: bucket, Prefix: prefix },
)) {
  for (const object of page.Contents ?? []) {
    keys.push(object.Key);
  }
}

const url = await getSignedUrl(
  s3,
  new GetObjectCommand({ Bucket: bucket, Key: key }),
  { expiresIn: 3600 }, // seconds; 7 days is the hard maximum
);
// Anyone holding this URL can read the object until it expires, with no
// credentials at all.

await s3.send(new DeleteObjectCommand({ Bucket: bucket, Key: key }));