Snippet for doing auto-pagination of a DynamoDB scan with an async generator in NodeJS

dynamodb-auto-paginate-scan.ts

import { DocumentClient } from "aws-sdk/lib/dynamodb/document_client";

export async function* autoPaginateScan<I extends DocumentClient.AttributeMap>(
  docClient: DocumentClient,
  params: DocumentClient.ScanInput
) {
  while (true) {
    const data = await docClient.scan(params).promise();

    if (data.Items && data.Items.length) {
      const items = data.Items as I[];
      yield* items;
    }

    if (data.LastEvaluatedKey === undefined) {
      break;
    }

    params = { ...params, ExclusiveStartKey: data.LastEvaluatedKey };
  }
}

example.ts

type Item = { id: string; name: string; description?: string };

const itemSeq = fullScanSeq<Item>(docClient, {
  TableName: "items",
  FilterExpression: "attribute_not_exists(#d)",
  ExpressionAttributeNames: { "#d": "description" }
});

for await (let item of items) {
  console.log(`item: id=${item.id}, name=${item.name}`);
}

These snippets are for:

• the dynamodb-full-scan github repo
• related blog post on auto-pagination using async generators