const params = {

  Bucket: bucket_name,

  Key: 'test.txt'

}

s3.headObject(params, function(err, data) {

   console.log(data)

});

Output:

{

  AcceptRanges: 'bytes',

  LastModified: 2020-09-03T15:53:09.000Z,

  ContentLength: 19,

  ETag: '"cb4f442e395bcf0bec578533e171537c"',

  VersionId: 'L.OyYlW2AOEcarfmoKlLUbAbOc8X45.',

  ContentType: 'application/octet-stream',

  Metadata: { 'custom-data': 'whatever', 'x-amz-meta-hello-world': 'data    here' }

}