在CreateMultipartUploadCommand返回的Promise中添加对ETag的解析，并在调用CompleteMultipartUploadCommand时将其作为参数传递。

示例代码如下：

const { S3Client, CreateMultipartUploadCommand, UploadPartCommand, CompleteMultipartUploadCommand } = require('@aws-sdk/client-s3');
const { Readable } = require('stream');

const s3 = new S3Client({ region: 'us-east-1' });

async function uploadFile(bucketName, key, filePath) {
   const fileStream = fs.createReadStream(filePath);

   // 创建Initiate Multipart Upload请求
   const initResult = await s3.send(new CreateMultipartUploadCommand({ Bucket: bucketName, Key: key }));

   const parts = [];

   // 分块上传
   for await (const part of uploadParts(initResult.UploadId, fileStream)) {
      parts.push(part);
   }

   // 完成Multipart Upload请求
   const completeResult = await s3.send(new CompleteMultipartUploadCommand({
      Bucket: bucketName, 
      Key: key, 
      UploadId: initResult.UploadId,
      MultipartUpload: { Parts: parts }
   }));

   return completeResult.Location;
}

async function* uploadParts(uploadId, fileStream) {
   let partNo = 0;

   while (true) {
      const chunk = await getFileChunk(fileStream);
      if (!chunk || chunk.length === 0) {
         break;
      }

      const uploadResult = await s3.send(new UploadPartCommand({
         Bucket: bucketName,
         Key: key,
         UploadId: uploadId,
         Body: chunk,
         PartNumber: ++partNo
      }));

      console.log(`Uploaded part ${partNo}: ${uploadResult.ETag}`);

      yield { ETag: uploadResult.ETag, PartNumber: partNo };
   }
}

function getFileChunk(fileStream) {
   return new Promise(resolve => {
      const readable = new Readable({
         read() {
            const chunk = fileStream.read(1024 * 1024);
            if (chunk) {
               this.push(chunk);
            } else {
               this.push(null);
            }
            resolve(chunk);
         }
      });
      readable.on('error', () => resolve(null));
   });
}