@prsm/db

A lightweight, in-memory document database for smaller projects. You can think of this as MongoDB's little brother.

Installation

npm i @prsm/db

API overview

For a more thorough API reference, please look at the tests in this repository.

Creating a collection

A collection is just a .json file.

import { Collection } from "@prism/db";

type Planet = {
  planet: string;
  diameter: number;
  population?: number;
  temp: {
    avg: number;
  };
};

// from `./.data` load or create `planets.json`
const collection = new Collection<Planet>(".data", "planets");

Inserting

collection.insert({ planet: "Mercury", diameter: 4880, temp: { avg: 475 } });
collection.insert([
  { planet: "Venus", diameter: 12_104, temp: { avg: 737_000 } },
  { planet: "Earth", diameter: 12_742, temp: { avg: 288 } },
]);

Finding

// finds Earth document
collection.find({ avg: 288 });
collection.find({ planet: "Earth" });

// finds Venus and Earth documents
collection.find({ diameter: { $gt: 12_000 } });

// finds Mercury and Earth documents
collection.find({ temp: { avg: { $lt: 1_000 } } });

// finds Mercury and Earth documents
collection.find({ $and: [{ avg: { $gt: 100 } }, { avg: { $lt: 10_000 } }] });

Updating

Any queries that work with .find work with .update.

// increase population, creating the property if it doesn't exist.
collection.update({ planet: "Earth" }, { $inc: { population: 1 } });

Removing

Any queries that work with .find work with .remove.

// remove every planet except Earth
collection.remove({ $not: { planet: "Earth" } });

Query options

find, update and remove accept a QueryOptions object.

{
  /** When true, attempts to deeply match the query against documents. */
  deep: boolean;

  /** Provide fallback values for null or undefined properties */
  ifNull: Record<string, any>;

  /** Provide fallback values for 'empty' properties ([], {}, "") */
  ifEmpty: Record<string, any>;

  /** Provide fallback values for null, undefined, or 'empty' properties. */
  ifNullOrEmpty: Record<string, any>;

  /**
   * -1 || 0: descending
   *  1: ascending
   */
  sort: { [property: string]: -1 | 0 | 1 };

  /**
   * Particularly useful when sorting, `skip` defines the number of documents
   * to ignore from the beginning of the result set.
   */
  skip: number;

  /** Determines the number of documents returned. */
  take: number;

  /**
   * 1: property included in result document
   * 0: property excluded from result document
   */
  project: {
    [property: string]: 0 | 1;
  };

  aggregate: {
    [property: string]:
      Record<"$floor", string> |
      Record<"$ceil", string> |
      Record<"$sub", (string|number)[]> |
      Record<"$mult", (string|number)[]> |
      Record<"$div", (string|number)[]> |
      Record<"$add", (string|number)[]>;
  };

  join: Array<{
    /** The collection to join on. */
    collection: Collection<any>;

    /** The property containing the foreign key(s). */
    from: string;

    /** The property on the joining collection that the foreign key should point to. */
    on: string;

    /** The name of the property to be created while will contain the joined documents. */
    as: string;

    /** QueryOptions that will be applied to the joined collection. */
    options?: QueryOptions;
  }>;
}

ifNull

// [
//   { a: 1, b: 2, c: 3 },
// ];

collection.find({ a: 1 }, { ifNull: { d: 4 } });

// [
//   { a: 1, b: 2, c: 3, d: 4 },
// ];

ifEmpty

// [
//   { a: 1, b: 2, c: 3, d: "  " },
//   { a: 1, b: 2, c: 3, d: [] },
//   { a: 1, b: 2, c: 3, d: {} },
// ];

collection.find({ a: 1 }, { ifEmpty: { d: 4 } });

// [
//   { a: 1, b: 2, c: 3, d: 4 },
//   { a: 1, b: 2, c: 3, d: 4 },
//   { a: 1, b: 2, c: 3, d: 4 },
// ];

Sorting

// [
//   { name: "Deanna Troi", age: 28 },
//   { name: "Worf", age: 24 },
//   { name: "Xorf", age: 24 },
//   { name: "Zorf", age: 24 },
//   { name: "Jean-Luc Picard", age: 59 },
//   { name: "William Riker", age: 29 },
// ];

collection.find({ age: { $gt: 1 } }, { sort: { age: 1, name: -1 } });
//                                                  └─ asc    └─ desc

// [
//   { name: "Zorf", age: 24 },
//   { name: "Xorf", age: 24 },
//   { name: "Worf", age: 24 },
//   { name: "Deanna Troi", age: 28 },
//   { name: "William Riker", age: 29 },
//   { name: "Jean-Luc Picard", age: 59 },
// ];

Skip & take (i.e. LIMIT)

Mostly useful when paired with sort.

// [
//   { a: 1, b: 1, c: 1 },
//   { a: 2, b: 2, c: 2 },
//   { a: 3, b: 3, c: 3 },
// ];

collection.find({ a: { $gt: 0 } }, { skip: 1, take: 1 });

// [
//   { a: 2, b: 2, c: 2 },
// ];

Projection

The ID property of a document is always included unless explicitly excluded.

Implicit exclusion

When all projected properties have a value of 1, this is "implicit exclusion" mode.

In this mode, all document properties that are not defined in the projection are excluded from the result document.

// [
//   { a: 1, b: 1, c: 1 },
// ];

collection.find({ a: 1 }, { project: { b: 1 } });

// [
//   { _id: .., b: 1 },
// ];

Implicit inclusion

When all projected properties have a value of 0, this is "implicit inclusion" mode.

In this mode, all document properties that are not defined in the projection are included from the result document.

// [
//   { a: 1, b: 1, c: 1 },
// ];

collection.find({ a: 1 }, { project: { b: 0 } });

// [
//   { _id: .., a: 1, c: 1 },
// ];

Explicit

In the only remaining case, all document properties are included unless explicitly removed with a 0.

This is effectively the same behavior as implicit inclusion.

// [
//   { a: 1, b: 1, c: 1 },
// ];

collection.find({ a: 1 }, { project: { b: 1, c: 0 } });

// [
//   { _id: .., a: 1, b: 1 },
// ];

Aggregation

// [
//   { math: 72, english: 82, science: 92 },
//   { math: 60, english: 70, science: 80 },
//   { math: 90, english: 72, science: 84 }
// ]

collection.find(
  {},
  {
    aggregate: {
      total: { $add: ["math", "english", "science"] },
      average: { $div: ["total", 3] },
    },
    project: {
      _id: 0,
      total: 0,
    },
  }
);

// [
//   { math: 72, english: 82, science: 92, average: 82 },
//   { math: 60, english: 70, science: 80, average: 70 },
//   { math: 90, english: 72, science: 84, average: 82 },
// ]

Joining

// "users" collection

// [
//   { name: "Alice", purchasedTicketIds: [1, 2] },
// ];

// "tickets" collection

// [
//   { _id: 0, seat: "A1" },
//   { _id: 1, seat: "B1" },
//   { _id: 2, seat: "C1" },
//   { _id: 3, seat: "D1" },
// ];

users.find(
  { name: "Alice" },
  {
    join: [
      {
        collection: tickets,
        from: "purchasedTicketIds",
        on: "_id",
        as: "tickets",
        options: {
          project: { _id: 0 },
        },
      },
    ],
  }
);

// [
//   {
//     name: "Alice",
//     purchasedTicketIds: [1, 2],
//     tickets: [
//       { seat: "B1" },
//       { seat: "C1" },
//     ],
//   },
// ];

join allows for QueryOptions which in turn alows for join. This means that joins can be chained for more complex relationships between collections.

users.find(
  { .. },
  {
    join: [{
      collection: tickets,
      options: {
        join: [{
          collection: seats,
          options: {
            join: [{
              collection: auditoriums,
            }]
          }
        }]
      }
    }]
  }
);

Misc

Renaming builtin property names

The default property names for document ID (default _id), "created at" (default _created_at) and "updated at" (default _updated_at) timestamps can all be changed.

import { ID_KEY, CREATED_AT_KEY, UPDATED_AT_KEY } from "@prism/db";

ID_KEY = "id";
CREATED_AT_KEY = "createdAt";
UPDATED_AT_KEY = "updatedAt";

If you do this, make sure to do it at the beginning of collection creation.

Documents

The returned value from find, update and remove is always an array, even when there are no results.