Enhanced Maps are a data structure that can be used to store data in memory that can also be saved in a database behind the scenes. The data is synchronized to the database automatically, seamlessly, and asynchronously so it should not adversely affect your performance compared to using Maps for storage.

A: Enmaps are the Javascript Map() data structure with additional utility methods.

A: With the use of the optional providers modules, any data added to the Enmap is stored not only in temporary memory but also backed up in a local database.

A: In its initial implementation, upon loading Enmap, all key/value pairs are loaded in memory. The size of the memory used is directly proportional to the size of your actual database.

Future versions will have ways to load partial or temporary values, etc.

To use Enmap, install it via NPM:

npm i enmap

Inside your script, initialize a new Enmap:

const Enmap = require("enmap");

// Initialize an instance of Enmap
const myCollection = new Enmap();

// Adding data is simply a `set` command: 
myCollection.set("myKey", "a value");

// Getting a value is done by key 
let result = myCollection.get("myKey");

Persistence requires an additional Provider module.

Official Enmap Providers:

• Enmap-SQLite Note: Against all odds, this provider DOES support sharding!
• Enmap-Rethink Note: Obviously, supports sharding.
• Enmap-PGSQL Note: That's shorthand for "Postgresql". Supports sharding of course.
• Enmap-Mongo Note: Yay, MongoDB! Supports sharding, duh.
• Enmap-Level Note: LevelDB does not support multiple processes or shards!

The following example uses Enmap-SQLite

// Load Enmap
const Enmap = require('enmap');

// Load EnmapSQLite
const EnmapSQLite = require('enmap-sqlite');

// Initialize the sqlite database with a table named "test"
const provider = new EnmapSQLite({ name: 'test' });

// Initialize the Enmap with the provider instance.
const myColl = new Enmap({ provider: provider });

// Persistent providers load in an **async** fashion and provide a handy defer property:

myColl.defer.then(() => {
    // all data is loaded now.
    console.log(myColl.size + "keys loaded");
});

// You can also await it if your function is async: 
(async function() {
    await myColl.defer;
    console.log(myColl.size + "keys loaded");
    // Do stuff here!
}());

// Persistent collections should be **closed** before shutdown: 
await myColl.db.close(); // or level.close() works too!

To account for people that might use a large number of enmaps in the same project, I've created a new multi() method that can be used to instanciate multiple peristent enmaps together.

The method takes 3 arguments:

• An array of names for the enmaps to be created.
• A Provider (not instanciated), from any of the available ones.
• An options object containing any of the options needed to instanciate the provider. Do not add name to this, as it will use the names in the array instead.

The method returns an object where each property is a new fully-started Enmap that can be used as you would normally.

Below, an example that uses destructuring to fit all in one nice line:

const Enmap = require('enmap');
const Provider = require('enmap-mongo');
const { settings, tags, blacklist, langs } = Enmap.multi(['settings', 'tags', 'blacklist', 'langs'], Provider, { url: "mongodb://localhost:27017/enmap" });

Note that this uses a static method which means you should NOT call new Enmap() yourself, it's done within the method.

Reading and writing data from an enmap is as simple as from a regular map. Note that the example uses a persistent enmap, but the set and get method will work for non-persistent enmaps too. Obviously though, those values won't be persistent through reboot if you don't give a provider.

const Enmap = require('enmap');
const EnmapSQLite = require('enmap-sqlite');
// Oh look a shortcut to initializing ;)
const myColl = new Enmap({ provider: new EnmapSQLite({ name: 'test' }) });

(async function() {
    await myColl.defer;
    console.log(myColl.size + 'keys loaded');

    // Setting data is done with a key and value.
    myColl.set('simplevalue', 'this is a string');
    
    // enmap supports any **primitive** type.
    myColl.set('boolean', true);
    myColl.set('integer', 42);
    myColl.set('null', null);

    // enmap can retrieve items at any time
    const simplevalue = myColl.get('simplevalue'); // 'this is a string'
    const myboolean = myColl.get('boolean'); // true
    if(myColl.get('boolean')) console.log('yay!') // prints 'yay!' to the console.

    // You can **change** the value of a key by loading it, editing it,
    // then setting it **back** into enmap. There's no "update" function
    // it just overrides the data through the same set method: 
    myColl.set('someobject', {blah: "foo", thing: "amajig"});
    console.log(myColl.get('someobject')) // prints the object to console.

    const myObject = myColl.get('someobject'); // value is now the object with 2 properties.
    myObject.thing = "amabob"; // value of temporary object is now {blah: "foo", thing: "amabob"}
    myColl.set('someobject', myObject); // only now is it actually written correctly.
}());

Because of how javascript works, doing something like myColl.get('myobject').blah = 'meh' actually works. HOWEVER that does not trigger persistence saves even though in memory it actually does change the enmap. "fixing" this would require some "monitor" on each value which is most definitely not the sort of overhead I want to add to this code. JavaScript wasn't built for that sort of thing in mind.

A enhanced Map structure with additional utility methods. Can be made persistent

Kind: global class
Extends: Map

• Enmap ⇐ Map
  • .close()
  • .set(key, val, save) ⇒ Map
  • .getProp(key, prop) ⇒ *
  • .setProp(key, prop, val, save) ⇒ Map
  • .hasProp(key, prop) ⇒ boolean
  • .setAsync(key, val) ⇒ Map
  • .delete(key, bulk)
  • .deleteAsync(key, bulk)
  • .array() ⇒ Array
  • .keyArray() ⇒ Array
  • .random([count]) ⇒ * | Array.<*>
  • .randomKey([count]) ⇒ * | Array.<*>
  • .findAll(prop, value) ⇒ Array
  • .find(propOrFn, [value]) ⇒ *
  • .exists(prop, value) ⇒ boolean
  • .filter(fn, [thisArg]) ⇒ Enmap
  • .filterArray(fn, [thisArg]) ⇒ Array
  • .map(fn, [thisArg]) ⇒ Array
  • .some(fn, [thisArg]) ⇒ boolean
  • .every(fn, [thisArg]) ⇒ boolean
  • .reduce(fn, [initialValue]) ⇒ *
  • .clone() ⇒ Enmap
  • .concat(...enmaps) ⇒ Enmap
  • .deleteAll(bulk)
  • .deleteAllAsync(bulk)
  • .equals(enmap) ⇒ boolean

Shuts down the underlying persistent enmap database.

Kind: instance method of Enmap

Kind: instance method of Enmap
Returns: Map - The Enmap.

Returns the specific property within a stored value. If the value isn't an object or array, returns the unchanged data If the key does not exist or the value is not an object, throws an error.

Kind: instance method of Enmap
Returns: * - The value of the property obtained.

Modify the property of a value inside the enmap, assuming this value is an object or array. This is a shortcut to loading the key, changing the value, and setting it back. If the key does not exist or the value is not an object, throws an error.

Kind: instance method of Enmap
Returns: Map - The EnMap.

Returns whether or not the property exists within an object or array value in enmap. If the key does not exist or the value is not an object, throws an error.

Kind: instance method of Enmap
Returns: boolean - Whether the property exists.

Kind: instance method of Enmap
Returns: Map - The Enmap.

Kind: instance method of Enmap

Kind: instance method of Enmap

Creates an ordered array of the values of this Enmap, and caches it internally. The array will only be reconstructed if an item is added to or removed from the Enmap, or if you change the length of the array itself. If you don't want this caching behaviour, use Array.from(enmap.values()) instead.

Kind: instance method of Enmap

Creates an ordered array of the keys of this Enmap, and caches it internally. The array will only be reconstructed if an item is added to or removed from the Enmap, or if you change the length of the array itself. If you don't want this caching behaviour, use Array.from(enmap.keys()) instead.

Kind: instance method of Enmap

Obtains random value(s) from this Enmap. This relies on array, and thus the caching mechanism applies here as well.

Kind: instance method of Enmap
Returns: * | Array.<*> - The single value if count is undefined, or an array of values of count length

Obtains random key(s) from this Enmap. This relies on keyArray, and thus the caching mechanism applies here as well.

Kind: instance method of Enmap
Returns: * | Array.<*> - The single key if count is undefined, or an array of keys of count length

Searches for all items where their specified property's value is identical to the given value (item[prop] === value).

Kind: instance method of Enmap

Example

enmap.findAll('username', 'Bob');

Searches for a single item where its specified property's value is identical to the given value (item[prop] === value), or the given function returns a truthy value. In the latter case, this is identical to Array.find(). All Enmap used in Discord.js are mapped using their id property, and if you want to find by id you should use the get method. See MDN for details.

Kind: instance method of Enmap

Example

enmap.find('username', 'Bob');

Example

enmap.find(val => val.username === 'Bob');

Searches for the existence of a single item where its specified property's value is identical to the given value (item[prop] === value). Do not use this to check for an item by its ID. Instead, use enmap.has(id). See MDN for details.

Kind: instance method of Enmap

Example

if (enmap.exists('username', 'Bob')) {
 console.log('user here!');
}

Identical to Array.filter(), but returns a Enmap instead of an Array.

Kind: instance method of Enmap

Identical to Array.filter().

Kind: instance method of Enmap

Identical to Array.map().

Kind: instance method of Enmap

Identical to Array.some().

Kind: instance method of Enmap

Identical to Array.every().

Kind: instance method of Enmap

Identical to Array.reduce().

Kind: instance method of Enmap

Creates an identical shallow copy of this Enmap.

Kind: instance method of Enmap
Example

const newColl = someColl.clone();

Combines this Enmap with others into a new Enmap. None of the source Enmaps are modified.

Kind: instance method of Enmap

Example

const newColl = someColl.concat(someOtherColl, anotherColl, ohBoyAColl);

Calls the delete() method on all items that have it.

Kind: instance method of Enmap

Calls the delete() method on all items that have it.

Kind: instance method of Enmap

Checks if this Enmap shares identical key-value pairings with another. This is different to checking for equality using equal-signs, because the Enmaps may be different objects, but contain the same data.

Kind: instance method of Enmap
Returns: boolean - Whether the Enmaps have identical contents