TynamoDB

An abstracted DynamoDB document client and expression dsl.

Getting Started

This package is based on the AWS SDK for JavaScript v3. For more information about AWS SDK, please check the official documentation.

• https://github.com/aws/aws-sdk-js-v3
• https://github.com/aws/aws-sdk-js-v3/tree/main/clients/client-dynamodb
• https://github.com/aws/aws-sdk-js-v3/tree/main/lib/lib-dynamodb

Prerequisites

The following versions of Node.js and TypeScript are required:

• Node.js 16 or higher
• TypeScript 4.7 or higher

This package is pure ESM, and you must configure your project to use the ESM package.

Installation

npm install tynamodb @aws-sdk/client-dynamodb @aws-sdk/lib-dynamodb

Usage

First you need to create a client.

import { TynamoDB } from 'tynamodb';

const tynamodb: TynamoDB = new TynamoDB();

Instead of using the default configuration, you can configure the client yourself.

import { DynamoDBClient } from '@aws-sdk/client-dynamodb';
import { DynamoDBDocument } from '@aws-sdk/lib-dynamodb';
import { TynamoDB } from 'tynamodb';

const client: DynamoDBClient = new DynamoDBClient({ ... });
const documentClient: DynamoDBDocument = DynamoDBDocument.from(client, { ... });
const tynamodb: TynamoDB = new TynamoDB(documentClient);

You can call operations with expression dsl.

import { attribute, value } from 'tynamodb';

await tynamodb.put({
    tableName: 'example',
    item: {
        key: 'value',
        foo: 'bar',
    },
    conditionExpression: attribute('key').notExists(),
});

Expression DSL

Expression dsl makes it easy to write expressions and handle placeholders easily.

import { and, attribute, update, value } from 'tynamodb';

await tynamodb.update({
    tableName: 'example',
    key: {
        key: 'value',
    },
    conditionExpression: and(
        attribute('foo').equal(value('bar')),
        attribute('foo').notEqual(value('baz')),
    ),
    updateExpression: update(
        attribute('foo').set(value('baz')),
    ),
});

Duplicate expression attribute names and values ​​are automatically optimized as follows:

{
    ConditionExpression: '#0 = :0 AND #0 <> :1',
    UpdateExpression: 'SET #0 = :1',
    ExpressionAttributeNames: {
        '#0': 'foo',
    },
    ExpressionAttributeValues: {
        ':0': 'bar',
        ':1': 'baz',
    },
}

If you are not using the TynamoDB client, you must evaluate the expression yourself, as follows:

import { ExpressionAttributeNames, ExpressionAttributeValues, and, attribute, update, value } from 'tynamodb';

const conditionExpression: Expression = and(
    attribute('foo').equal(value('bar')),
    attribute('foo').notEqual(value('baz')),
);
const updateExpression: Expression = update(
    attribute('foo').set(value('baz')),
);

const names: ExpressionAttributeNames = new ExpressionAttributeNames();
const values: ExpressionAttributeValues = new ExpressionAttributeValues();

expect(conditionExpression.evaluate(names, values)).toBe('#0 = :0 AND #0 <> :1');
expect(updateExpression.evaluate(names, values)).toBe('SET #0 = :1');

expect(names.serialize()).toStrictEqual({
    '#0': 'foo',
});
expect(values.serialize()).toStrictEqual({
    ':0': 'bar',
    ':1': 'baz',
});

Expression dsl prevents invalid expressions from being written. For example, the following code fails to compile:

import { attribute, update, value } from 'tynamodb';

update(
    attribute('foo').equal(value('bar')),
);

Nested attribute expressions and attribute expressions containing special characters can be created as follows:

attribute('a', 'b', 0, 'c', 1, 2, 'd.e', '34');

Created attribute expression are evaluated as follows:

{
    Expression: '#0.#1[0].#2[1][2].#3.#4',
    ExpressionAttributeNames: {
        '#0': 'a',
        '#1': 'b',
        '#2': 'c',
        '#3': 'd.e',
        '#4': '34',
    },
}

License

Distributed under the MIT License. See the LICENSE file for more details.