DynamicUpdateExpressionFromObject.ts

interface DynamoUpdateParams {
  UpdateExpression: string;
  ExpressionAttributeNames: Record<string, string>;
  ExpressionAttributeValues: Record<string, unknown>;
}

export const DynamicUpdateExpressionFromObject = (map: Record<string, unknown>): DynamoUpdateParams => {
  const ExpressionAttributeNames: Record<string, string> = Object.keys(map)
    .reduce((acc, curr) => ({ ...acc, ...{ [`#${curr}`]: curr } }), {});
  const UpdateExpression: string = Object.values(ExpressionAttributeNames)
    .reduce((acc, curr) => `${acc} #${curr} = :${curr},`, 'SET').slice(0, -1);
  const ExpressionAttributeValues = Object.entries(map)
    .reduce((acc, [key, value]) => ({ ...acc, ...{ [`:${key}`]: value } }), {});

  return {
    UpdateExpression,
    ExpressionAttributeNames,
    ExpressionAttributeValues,
  };
};

Example Usage

export const updateItem = async (pk: string, item: Partial<Item>): Promise<void> => {
  const updateParams = DynamicUpdateExpressionFromObject(item);

  await dynamoDBClient.update({
    TableName: process.env.DYNAMODB_TABLE,
    Key: {
      pk,
      sk: `item:${item.id}`,
    },
    ...updateParams,
  }).promise();
};