Now that we have a functional Enmap structure (which we'll always refer to as myEnmap), we're ready to start writing data to it, and getting data from it.

The code samples on this page assume that you have correctly initialized myEnmap, and awaited its initialization if it's persistent.

Writing Data

In terms of Enmap, "writing", "adding" and "editing" data is essentially the same thing. When using the basic set() method, if the key does not exist it's created, and if it does, it's modified.

Enmap supports most native JavaScript data types, with a few small exceptions.

• Complex objects like Set(), Map(), etc, are not supported.

• Class instances and Functions are not supported.

As a general rule, except for null and undefined, anything that can be handled by JSON.stringify() will work as expected in Enmap. This includes:

• String

• Number

• Integer

• Boolean

• Object

• Array

Objects and Arrays are a little more complex to deal with, so they have their own page. See Working with Objects for more information.

The usage for the set() method is simple:

<Enmap>.set(key, value);

• key must be a string or integer. A key should be unique, otherwise it will be overwritten by new values using the same key.

• value must be a supported native data type as mentioned above.

Here are a few examples of writing simple data values:

myEnmap.set('boolean', true);
myEnmap.set('integer', 42);
myEnmap.set('someFloat', 73.2345871);
myEnmap.set("Test2", "test2");

Retrieving Data

Getting data back from an Enmap is just as simple as writing to it. All you need is the key of what you want to retrieve, and you get its value back!

const floatValue = myEnmap.get('someFloat');
const test = myEnmap.get('Test2');

// you can even use booleans in conditions: 
if(myEnmap.get('boolean')) {
  // boolean is true!
}

That's pretty much it for only retrieiving a single data value. There are more complex operations that are available, take a look at Array Methods for the more advanced things you can do on Enmap's data!

Persistence requires an additional Provider module.

Official Enmap Providers:

• Enmap-SQLite: Recommended, supports sharding locally.

• Enmap-Rethink: Best for sharding if you can install a rethinkdb server. Supports updating from the database on all shards (enmap-rethink 2.1.0 and higher)

• Enmap-PGSQL: Postgresql database provider. Supports Sharding.

• Enmap-Mongo: Mongodb database provider. Supports Sharding.

• Enmap-Level: Sort of not recommended at this point, doesn't support sharding, no longer the most efficient/faster provider.

When using any provider, it's very important to understand that it takes time to load the data from the database. Certain providers also take some time to even open the database connection, and that's also something to consider.

Using defer

To make sure that all your data is loaded before you start working, Enmap provides a handy property called defer , which is a promise that is resolved once the provider is ready and all the data has been loaded into memory. There are a few ways to use defer , since it's a promise.

// 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();

Enmap stands for "Enhanced Map", and is a data structure based on the native JavaScript Map() structure with additional helper methods from the native Array() structure.

Enmap also offers persistence, which means it will automatically save everything to save to it in a database, in the background, without any additional code or delays.

Why Enmap?

While there are other better-known systems that offer some features of Enmap, especially caching in memory, Enmap is targetted specifically to newer users of JavaScript that might not want to deal with complicated systems like Redis for caching, or database queries.

Advantage/Disadvantage

Here are some advantages of using Enmap:

• Simple to Install: Enmap itself only requires a simple npm install command to install and use, and a single line to initialize. When using persistent providers, some additional pre-requisites are necessary. See Installation for details.

• Simple to Use: Basic enmap usage can be completely done with 1-2 lines of initalization, and 3 commands, set(), get() and delete().

• Very Fast: Since Enmap resides in memory, accessing its data is blazing fast (as fast as Map() is). Even with persistence, Enmap still only accesses data from memory so you get it almost instantly.

Some disadvantages, compared to using a database connection directly:

• More memory use: Since Enmap resides in memory and (by default) all its data is loaded when it starts, your entire data resides in RAM. When using a large amount of data on a low-end computer or VPS, this might be an issue for some users.

• Limited power: You can have multiple Enmap "tables" loaded in your app, but they do not and cannot have relationships between them. Basically, one enmap value can't refer to another value in another enmap. This is something databases can be very good at, but due to the simplistic nature of Enmap, it's not possible here.

• Lack of scalability: Enmap is great for small apps that require a simple key/value storage. However, a scalable app spread over multiple processes, shards, or clusters, will be severely limited by Enmap as it cannot update itself from the database on change - one process would not be aware of another process' changes.

Some quick docs:

enmap.math(key, operation, operator, [objectPath])

Possible Operators (accepts all variations listed below, as strings):

• +, add, addition: Increments the value in the enmap by the provided value.

• -, sub, subtract: Decrements the value in the enmap by the provided value.

• *, mult, multiply: Multiply the value in the enmap by the provided value.

• /, div, divide: Divide the value in the enmap by the provided value.

• %, mod, modulo: Gets the modulo of the value in the enmap by the provided value.

• ^, exp, exponential: Raises the value in the enmap by the power of the provided value.

enmap.inc(key, [objectPath])

enmap.dec(key. [objectPath])

While Enmap is a Map enhanced with Array methods, Enmap also offers some enhanced array methods for the data stored inside of it. Talk about ArrayCeption!

So what do I mean by methods for your stored data? I mean that you can store arrays inside Enmap, and directly push, pull, add and remove from those arrays. There are methods to work both on direct arrays, as well as arrays stored inside of an object.

Let's take a look at two example entries in enmap that we can use. The first is a direct array, the second is an array inside an object.

Adding to the array

There are two methods to push to an array, one for simple arrays and one for arrays inside objects. Pushing in an enmap array is the same as a regular array push: it adds the element to the end of the array.

Removing from the array

Similarly, you can remove from an array. Note, however, that this will only work if you're removing a string or number. Removing an object from an array is not supported.

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.

Below, an example that uses destructuring:

Pre-Requisites

In order to install Enmap, you'll need a few things installed on your machine. First off, you need NodeJS (version 8 or higher required). For Windows and MacOS, simply download and install from the website. For Linux, see this page for installation.

Enmap v3 is no longer maintained on NPM and is only available on Github. You will need to install a git tool on your computer to install it.

Next, enmap has a specific pre-requisite which is needed for the sqlite dependency. How to install these depends on your operating system, so see below for instructions:

npm -g --add-python-to-path install windows-build-tools node-gyp

Installing enmap

To install Enmap in your project, all you need to to is run the following command in your project folder:

npm i eslachance/enmap#v3

This may take a few minutes, then you're ready to use it.

For this purpose, I surrepticiously added a new option somewhere around Enmap 2.0 called "fetchAll", which defaults to "true" if you don't specify it - which is the old behaviour, and current default at the same time. But, if you set fetchAll to false in the Enmap options, data is not fetched on load.

What does it mean if the data isn't loaded?

If fetchAll is set to false, no data (by default) will be loaded from the database - the Enmap will be completely empty. This means that doing a .size check returns 0, looping and filtering doesn't return anything, and get() requests all return null.

Ok but... how's that useful? It's useful because if you don't need the data, it's not loaded. To load data, there are 2 different methods available.

Fetching Data

• enmap.fetchEverything() will, of course, fetch all the data from the database - this is the method that's called on init() if fetchAll is true. This means you can stagger your loading time, or that you can decide, later, under certain conditions, you do want to load everything.

• enmap.fetch(key) can fetch a single key from the database, saves it to enmap, and returns a promise with the fetched value.

• enmap.fetch([array, of, keys]) will fetch each key in the requested array, and return an array of [key, value] pairs for each fetched value.

That's it!

Yup. Those are the only things you really need to know for the current version of Enmap's fetchAll feature.

Upcoming Features:

I'm working on the following features in future versions of enmap, related to fetch methods:

• Add the ability to check if the DB has a key without fetching

• Add a method to uncache a key from enmap

• Add a method to count keys in the DB (like enmap.keyCount() maybe?)

• Figure out how to "fetch on query" without breaking the nonblocking nature of enmap.

Enmap is a great way to store structured data, and offers a few helper features that directly affect both objects and arrays.

Let's assume for a moment that we want to store the following data structure in Enmap:

const myStructure = {
  first: "blah",
  second: "foo",
  changeme: "initial",
  isCool: false
  sub: {
    yay: true,
    thing: "amagig"
  }
}

This structure has 5 "properties": first, second, changeme, isCool, sub. The sub property has 2 properties of its own, yay and thing.

To store this structure in Enmap, you can use a variable, or just straight-up write the object:

myEnmap.set("someObject", myStructure);

// Or directly the object
myEnmap.set("someObject", {first: "blah", ...});

// Works with arrays, too!
myEnmap.set("someArray", ["one", "two", "three"]);

Note: All further methods require the value to be an object. If you attempt to get, set, modify or remove using the below methods and your value isn't an object, Enmap will throw an error.

Getting properties

Retrieving a specific property from an object is done through the get() method, by specifying both the key and the "path" to the property you want.

The exact method is <Enmap>.get(key, path).

const second = myEnmap.get("someObject", "second");
// returns "foo"

const thing = myEnmap.get("someObject", "sub.thing");
// returns true

// The path can be dynamic, too: 
const propToGet = "thing";
const blah = myEnmap.get("someObject", `sub.${propToGet}`);

Checking if a property exists

You can also check if a specific property exists or not. This is done through the has method, with a key, and path to the property:

myEnmap.has("someObject", "sub.thing"); // returns true

myEnmap.has("someObject", "heck"); // returns false.

Modifying Properties

There are a few various ways to modify properties of both Objects and Arrays. The very basic way to set a property on an object or array is through .set(key, value, path) like the following examples:

// Set an object property
myEnmap.set("someObject", "sub.blah", "newThing");

// Set an array property
myEnmap.set("someArray", "four", 3);

As you can see, setProp() and getProp() work on the same concept that the path can be as complex as you want.

Arrays have additional helper methods, you can see them here.

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");

Enmap ⇐ Map

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

Kind: global class Extends: Map

• Enmap ⇐ Map

  • instance

    • .fetchEverything() ⇒ Promise.

    • .fetch(keyOrKeys) ⇒ Promise.

    • .evict(keyOrArrayOfKeys)

    • .autonum() ⇒ number

    • .changed(cb)

    • .set(key, val, path) ⇒ Map

    • .setProp(key, path, val) ⇒ Map

    • .push(key, val, path, allowDupes) ⇒ Map

    • .pushIn(key, path, val, allowDupes) ⇒ Map

    • .math(key, operation, operand, path) ⇒ Map

    • .inc(key, path) ⇒ Map

    • .dec(key, path) ⇒ Map

    • .get(key, path) ⇒ *

    • .getProp(key, path) ⇒ *

    • .has(key, path) ⇒ boolean

    • .hasProp(key, path) ⇒ boolean

    • .delete(key, path)

    • .deleteProp(key, path)

    • .deleteAll(bulk)

    • .remove(key, val, path) ⇒ Map

    • .removeFrom(key, path, val) ⇒ Map

    • .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

    • .equals(enmap) ⇒ boolean

  • static

    • .multi(names, Provider, options) ⇒ Array.

    • .migrate(source, target)

enmap.fetchEverything() ⇒ Promise.

Fetches every key from the persistent enmap and loads them into the current enmap value.

Kind: instance method of Enmap Returns: Promise. - The enmap containing all values, as a promise..

enmap.fetch(keyOrKeys) ⇒ Promise.

Force fetch one or more key values from the enmap. If the database has changed, that new value is used.

Kind: instance method of Enmap Returns: Promise. - A single value if requested, or a non-persistent enmap of keys if an array is requested.

enmap.evict(keyOrArrayOfKeys)

Removes a key from the cache - useful when using the fetchAll feature.

Kind: instance method of Enmap

enmap.autonum() ⇒ number

Generates an automatic numerical key for inserting a new value.

Kind: instance method of Enmap Returns: number - The generated key number. Example

enmap.set(enmap.autonum(), "This is a new value");

enmap.changed(cb)

Function called whenever data changes within Enmap after the initial load. Can be used to detect if another part of your code changed a value in enmap and react on it.

Kind: instance method of Enmap

Example

enmap.changed((keyName, oldValue, newValue) => {
  console.log(`Value of ${key} has changed from: \n${oldValue}\nto\n${newValue});
});

enmap.set(key, val, path) ⇒ Map

Set the value in Enmap.

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

Example

// Direct Value Examples
enmap.set('simplevalue', 'this is a string');
enmap.set('isEnmapGreat', true);
enmap.set('TheAnswer', 42);
enmap.set('IhazObjects', { color: 'black', action: 'paint', desire: true });
enmap.set('ArraysToo', [1, "two", "tree", "foor"])

// Settings Properties
enmap.set('IhazObjects', 'color', 'blue'); //modified previous object
enmap.set('ArraysToo', 2, 'three'); // changes "tree" to "three" in array.

enmap.setProp(key, path, val) ⇒ Map

Modify the property of a value inside the enmap, if the value is an object or array. This is a shortcut to loading the key, changing the value, and setting it back.

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

enmap.push(key, val, path, allowDupes) ⇒ Map

Push to an array value in Enmap.

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

Example

// Assuming
enmap.set("simpleArray", [1, 2, 3, 4]);
enmap.set("arrayInObject", {sub: [1, 2, 3, 4]});

enmap.push("simpleArray", 5); // adds 5 at the end of the array
enmap.push("arrayInObject", "five", "sub"); adds "five" at the end of the sub array

enmap.pushIn(key, path, val, allowDupes) ⇒ Map

Push to an array element inside an Object or Array element in Enmap.

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

enmap.math(key, operation, operand, path) ⇒ Map

Executes a mathematical operation on a value and saves it in the enmap.

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

Example

// Assuming
points.set("number", 42);
points.set("numberInObject", {sub: { anInt: 5 }});

points.math("number", "/", 2); // 21
points.math("number", "add", 5); // 26
points.math("number", "modulo", 3); // 2
points.math("numberInObject", "+", 10, "sub.anInt");

enmap.inc(key, path) ⇒ Map

Increments a key's value or property by 1. Value must be a number, or a path to a number.

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

Example

// Assuming
points.set("number", 42);
points.set("numberInObject", {sub: { anInt: 5 }});

points.inc("number"); // 43
points.inc("numberInObject", "sub.anInt"); // {sub: { anInt: 6 }}

enmap.dec(key, path) ⇒ Map

Decrements a key's value or property by 1. Value must be a number, or a path to a number.

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

Example

// Assuming
points.set("number", 42);
points.set("numberInObject", {sub: { anInt: 5 }});

points.dec("number"); // 41
points.dec("numberInObject", "sub.anInt"); // {sub: { anInt: 4 }}

enmap.get(key, path) ⇒ *

Retrieves a key from the enmap. If fetchAll is false, returns a promise.

Kind: instance method of Enmap Returns: * - The value for this key.

Example

const myKeyValue = enmap.get("myKey");
console.log(myKeyValue);

const someSubValue = enmap.get("anObjectKey", "someprop.someOtherSubProp");

enmap.getProp(key, path) ⇒ *

Returns the specific property within a stored value. 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.

enmap.has(key, path) ⇒ boolean

Returns whether or not the key exists in the Enmap.

Kind: instance method of Enmap

Example

if(enmap.has("myKey")) {
  // key is there
}

if(!enmap.has("myOtherKey", "oneProp.otherProp.SubProp")) return false;

enmap.hasProp(key, path) ⇒ boolean

Returns whether or not the property exists within an object or array value in enmap.

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

enmap.delete(key, path)

Deletes a key in the Enmap.

Kind: instance method of Enmap

enmap.deleteProp(key, path)

Delete a property from an object or array value in Enmap.

Kind: instance method of Enmap

enmap.deleteAll(bulk)

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

Kind: instance method of Enmap

enmap.remove(key, val, path) ⇒ Map

Remove a value in an Array or Object element in Enmap. Note that this only works for values, not keys. Complex values such as objects and arrays will not be removed this way.

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

enmap.removeFrom(key, path, val) ⇒ Map

Remove a value from an Array or Object property inside an Array or Object element in Enmap. Confusing? Sure is.

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

enmap.array() ⇒ Array

Creates an ordered array of the values of this Enmap. 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

enmap.keyArray() ⇒ Array

Creates an ordered array of the keys of this Enmap 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

enmap.random([count]) ⇒ * | Array.

Obtains random value(s) from this Enmap. This relies on array.

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

enmap.randomKey([count]) ⇒ * | Array.

Obtains random key(s) from this Enmap. This relies on keyArray

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

enmap.findAll(prop, value) ⇒ Array

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');

enmap.find(propOrFn, [value]) ⇒ *

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](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map/get) for details.

Kind: instance method of Enmap

Example

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

Example

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

enmap.exists(prop, value) ⇒ boolean

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](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map/has) for details.

Kind: instance method of Enmap

Example

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

enmap.filter(fn, [thisArg]) ⇒ Enmap

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

Kind: instance method of Enmap

enmap.filterArray(fn, [thisArg]) ⇒ Array

Identical to Array.filter().

Kind: instance method of Enmap

enmap.map(fn, [thisArg]) ⇒ Array

Identical to Array.map().

Kind: instance method of Enmap

enmap.some(fn, [thisArg]) ⇒ boolean

Identical to Array.some().

Kind: instance method of Enmap

enmap.every(fn, [thisArg]) ⇒ boolean

Identical to Array.every().

Kind: instance method of Enmap

enmap.reduce(fn, [initialValue]) ⇒ *

Identical to Array.reduce().

Kind: instance method of Enmap

enmap.clone() ⇒ Enmap

Creates an identical shallow copy of this Enmap.

Kind: instance method of Enmap Example

const newColl = someColl.clone();

enmap.concat(...enmaps) ⇒ Enmap

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);

enmap.equals(enmap) ⇒ boolean

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

Enmap.multi(names, Provider, options) ⇒ Array.

Initialize multiple Enmaps easily.

Kind: static method of Enmap Returns: Array. - An array of initialized Enmaps.

Example

// Using local variables and the mongodb provider.
const Enmap = require('enmap');
const Provider = require('enmap-mongo');
const { settings, tags, blacklist } = Enmap.multi(['settings', 'tags', 'blacklist'], Provider, { url: "some connection URL here" });

// Attaching to an existing object (for instance some API's client)
const Enmap = require("enmap");
const Provider = require("enmap-mongo");
Object.assign(client, Enmap.multi(["settings", "tags", "blacklist"], Provider, { url: "some connection URL here" }));

Enmap.migrate(source, target)

Migrates an Enmap from version 3 or lower to a Version 4 enmap, which is locked to sqlite backend only. Version 4 uses a different way of storing data, so is not directly compatible with version 3 data. Note that this migration also makes the data unuseable with version 3, so it should only be used to migrate once.

Kind: static method of Enmap

Example

// This example migrates from enmap-mongo to the new format.
// Assumes: npm install enmap@3.1.4 enmap-sqlite@latest enmap-mongo@latest
const Enmap = require("enmap");
const Provider = require("enmap-mongo");
const SQLite = require("enmap-sqlite");

let options = {
 name: 'test',
 dbName: 'enmap',
 url: 'mongodb://username:password@localhost:27017/enmap'
};

const source = new Provider(options);
const target = new SQLite({"name": "points"});

Enmap.migrate(source, target);