LokiJS Collections

TypeScript port of lokiJS. As of version 0.22.0 of this project, lokiJS is no longer a dependency and a [email protected] is integrates directly into this project.

Usage

This project is designed to be imported using commonJs require(...) calls. To use this in a web app, it's currently setup to be required and then included in a bundle at build time.

Setup

Creating a database instance is the most involved task, once the database instance is created the rest is fairly straightfoward. You'll need a few things to create a lokijs-collection database:

• A database name
• Data models - one for each collection with schema information about the type of data being stored in each
• (optional) A database persister. You can use the DummyDataPersister in the 'test/' directory if you don't need to persist your data yet or aren't sure how a data persister works. You can use defaults for the rest of the settings, most of them work fine

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1. Example - Creating an in-memory database instance:

var InMemDbImpl = require("lokijs-collections/db-collections/InMemDbImpl");
var ModelDefinitionsSet = require("lokijs-collections/data-models/ModelDefinitionsSet");
var DtoPropertyConverter = require("@twg2/ts-twg2-ast-codegen/code-types/DtoPropertyConverter");

var databaseName = "...";

// two collection schemas or models, enables a lot of cool TypeScript type checking, fewer bugs, and easy constraint setup (i.e. not-null, unique, auto-generated)
var dataModels = {
    collection_1_name: {
        properties: DtoPropertyConverter.parseAndConvertTemplateMap({
            "id": { primaryKey: true, autoGenerate: true, type: "number" },
            "name": { type: "string" },
            "props": { type: "string[]" },
        })
    },
    collection_2_name: {
        properties: DtoPropertyConverter.parseAndConvertTemplateMap({
            "userId": { type: "string" },
            "note": { type: "string" },
            "timestamp": { autoGenerate: true, type: "Date" },
        })
    }
};

// create the DB instance, there are a lot of configurable settings, this one is using a dummy data persister, everything is in-memory
var dbInst = new InMemDbImpl(databaseName,
    { readAllow: true, writeAllow: true, compressLocalStores: false },
    "for-in-if",
    "collection_meta_data", false,
    ModelDefinitionsSet.fromCollectionModels(dataModels, null/*defaultDataTypes*/),
    (collectionName) => { return { ... }; },
    (obj, collection, dataModel) => {
        return Object.keys(obj);
        // or
        return dataModel.fieldNames;
    }
);

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2. Example - Creating a WebSQL database persister:

Note: the WebSqlPersister constructor has several parameters which are highly customizable, please read the class and constructor documentation for details.

var DbUtil = require("lokijs-collections/persisters/DbUtil");
var WebSqlSpi = require("lokijs-collections/persisters/WebSqlSpi");
var WebSqlPersister = require("lokijs-collections/persisters/WebSqlPersister");

// log to console or other error logger
var trace: WebSqlSpi.Trace = {
    log: (...args: any[]) => ...,
    error: (...args: any[]) => ...,
    text: (...args: any[]) => ...,
};

var sqlInst = WebSqlSpi.newWebSqlDb("persistent-websql-database", null, null, null,
    { trace: trace, logVerbosity: DbUtil.logLevels.ERROR });

var persister = new WebSqlPersister(sqlInst,
    trace,
    () => dbInst.listCollections(),
    (collName, data) => {
        var coll = dbInst.getCollection(collName, true);
        coll.insert(data);
        return coll;
    },
    (itm) => InMemDbImpl.cloneCloneDelete(itm, true),
    null,
    null,
    (err) => trace.error("storage error", err),
    [],
    []
);

You now have a working in-memory database using TypeScript. You can skip Example #2 if you do not wish to persist the in-memory database between page/application reloads. Checkout the 'test/' directory for usage examples.

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Project Structure

db-collections/

Contains 'DataCollection', a wrapper for a loki.js collection, add/remove/update functions modify the underlying loki.js collection. Also contains 'InMemDbImpl' which bridges the gap between an untyped loki.js instance and 'DataCollection'.

data-models/

ModelDefinitionsSet for creating and managing a group of DataCollectionModels using DtoModels or DataCollectionModels as a starting point.

change-trackers/

Collections and handlers for tracking lokijs collection changes (i.e. updates, additions, deletions).

key-constraints/

Collection meta-data and unique/primary key constraint handlers for 'DataCollection'. Includes:

• PrimaryKeyMaintainer for checking uniqueness of primary keys and/or generating numerical keys (i.e. 1, 2, 3, ...),
• NonNullKeyMaintainer for checking that fields have values

persisters/

'DataPersister' implementations and helper classes for persisting and restoring in-memory databases. Currently provides a WebSQL persister with an alpha level IndexedDB persister.