NodeJS : List S3 directories with AWS SDK

28 Feb 2018

When we use aws-sdk to list objects in s3 bucket it will list objects without any seperation between directories and files. The easy way to list all directories is to use Delimiter option.

Use Delimiter as / will result in list of CommonPrefixes in the response.

var AwsS3 = require ('aws-sdk/clients/s3');
const s3 = new AwsS3 ({
  accessKeyId: '',
  secretAccessKey: '',
  region: 'ap-south-1',
});

const listDirectories = params => {
  return new Promise ((resolve, reject) => {
    const s3params = {
      Bucket: 'bucket-name',
      MaxKeys: 20,
      Delimiter: '/',
    };
    s3.listObjectsV2 (s3params, (err, data) => {
      if (err) {
        reject (err);
      }
      resolve (data);
    });
  });
};

The above code will list the directories in the bucket root. The sample response will look like

{
  "IsTruncated": false,
  "Contents": [],
  "Name": "bucket-name",
  "Prefix": "",
  "Delimiter": "/",
  "MaxKeys": 20,
  "CommonPrefixes": [
    {
      "Prefix": "directory-1/"
    },
    {
      "Prefix": "directory-2/"
    },
    {
      "Prefix": "directory-3/"
    },
    {
      "Prefix": "directory-4/"
    }
  ],
  "KeyCount": 4
}

If we want to list the directories inside the one of the listed directory, Pass the directory name as Prefix.

const listDirectories = params => {
  return new Promise ((resolve, reject) => {
    const s3params = {
      Bucket: 'bucket-name',
      MaxKeys: 20,
      Delimiter: '/',
      Prefix: 'directory-1/'
    };
    s3.listObjectsV2 (s3params, (err, data) => {
      if (err) {
        reject (err);
      }
      resolve (data);
    });
  });
};

Hope it helped.
Let me know if you have any feedback or corrections via comments

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