NodeJS AWS Lambda ListObject returning empty array

I am new to AWS. I am creating a Scheduled lambda function using NodeJS. There I need to get all the objects in a folder and iterate through each, to check the last modified date and I want to delete old objects. But I am getting empty array in ListObject's Response Contents.

var s3 = new aws.S3();
exports.handler = (event, context, callback) => {

var params = {
    Bucket: 'bucket_name',
    Delimiter: '/',
    Prefix: 'folder_name',
    MaxKeys:100000
};
s3.listObjects(params, function(err, data) {
  if (err) console.log(err, err.stack); // an error occurred
  else
  {     
    var folderLength = data.Contents.length;
    data.Contents.forEach(function(metadata) {
      console.log('Key: ' + metadata.Key);
    });

  }
});
callback(null, 'Finished');
};

But in the response i am getting Contents: []. Can anyone tell me whats wrong?

via Salini