scan.js

const scanNext = lastEvaluatedKey =>
  scan(lastEvaluatedKey)
    .tap(data => {
      console.log(++counter, data.Count, data.LastEvaluatedKey);
    })
    .then(data =>
      data.LastEvaluatedKey ?
        scanNext(data.LastEvaluatedKey) :
        Promise.resolve()
    );

const somePromise = scanNext();

const scan = (lastEvaluatedKey) => {
 return dynamodb.scan({ TableName: process.env.TABLE, Limit: 20, ExclusiveStartKey: lastEvaluatedKey }).promise();
};