automaticUpdatedAtField.js

// automatically appends updatedAt timestamp
const update = async (updateParams) => {
    try {
        const timestamp = new Date().getTime();
        params.UpdateExpression = params.UpdateExpression + ', #updatedAt = :updatedAt';
        params.ExpressionAttributeNames['#updatedAt'] = 'updatedAt';
        params.ExpressionAttributeValues[':updatedAt'] = timestamp;
        return await db.update(updateParams).promise();
    }
    catch (error) { throw error; }
};

var params = {
    TableName: 'PRODUCTS_TABLE',
    Key: { "id": someProductId },
    ConditionExpression: 'id = :id AND createdBy = :createdBy',
    UpdateExpression: 'set #data.#price = :updatedPrice',
    ExpressionAttributeNames: { '#data': 'data', '#price': 'price' },
    ExpressionAttributeValues: { ':id': someProductId, ':updatedPrice': 3456.78, ':createdBy': creatorId }
};
try {
		await dynamoDB.update(params);
} catch (error) {
	  console.log(error);
}