AWS @aws-sdk/lib-dynamodb 'Cannot read property '0' of undefined'

Question

I try to leverage @aws-sdk/lib-dynamodb for simplifying data retrieval from AWS DynamoDB.

# aws.js
const {DynamoDBClient,ScanCommand} = require('@aws-sdk/client-dynamodb');
const { DynamoDBDocumentClient } = require('@aws-sdk/lib-dynamodb');
const { fromIni } = require('@aws-sdk/credential-provider-ini');
const client = new DynamoDBClient({
    credentials: fromIni({ profile: process.env.AWS_PROFILE }),
    region: process.env.AWS_DEFAULT_REGION,
});

const ddb_client = DynamoDBDocumentClient.from(client);

const listItemsDDB = async (params) => {
    try {
        const command = new ScanCommand(params);
        const data = await ddb_client.send(command);
        return data;
    } catch (err) {
        throw Error(err);
    }
};
module.exports = {listItemsDDB };

I import the functions into my rest_api.js. Everything is based on an express js application.

...trimmed...

app.get('/courses/:year/:location/:month', async (req, res, next) => {
    console.log(req.params);
    const payload = {
        TableName: ddb_calendar_name,
        FilterExpression: '#l = :loc and #m = :month and #y = :year',
        ExpressionAttributeValues: {
            ':loc': req.params.location,
            ':month': req.params.month,
            ':year': req.params.year,
        },
        ExpressionAttributeNames: {
            '#l': 'Location',
            '#m': 'Month',
            '#y': 'Year',
        },
    };
    try {
        const result = await aws.listItemsDDB(payload);
        return res.status(200).send(result.Items[0]);
    } catch (error) {
        next(error);
    }
});

My data looks like this:

{
  "Id": {
    "S": "02322f8f-05a7-4e27-aaf9-08129f3128ef"
  },
  "Location": {
    "S": "schildergasse"
  },
  "Month": {
    "S": "august"
  },
  "Year": {
    "S": "2021"
  }
}

I use a rest client to test the endpoints. After firing GET http://localhost:4000/courses/2021/schildergasse/august I receive:

Error: TypeError: Cannot read property '0' of undefined at Object.listItemsDDB (/Users/olivergoetz/fifi-calendar/server/aws.js:39:9) at processTicksAndRejections (node:internal/process/task_queues:96:5) at async /Users/olivergoetz/fifi-calendar/server/rest_api.js:221:18

What point to I miss here?

Answer 1

I imported the ScanCommand from the wrong library:

I had to change this:

const {DynamoDBClient,ScanCommand} = require('@aws-sdk/client-dynamodb');
const { DynamoDBDocumentClient } = require('@aws-sdk/lib-dynamodb');

to this:

const {DynamoDBClient} = require('@aws-sdk/client-dynamodb');
const { DynamoDBDocumentClient, ScanCommand } = require('@aws-sdk/lib-dynamodb');