js-singleton

A singleton wrapper for creating single instances of functions.

This module can wrap an arbitrary number of functions in the same Singleton meaning you can init everything you need and then just use require('js-singleton'); in other modules and it will work just fine.

Examples

Simple example in multi mode

const Singleton = require('js-singleton')();

function Person(firstname, lastname){
  this.firstname = firstname;
  this.lastname = lastname;
}

var person = Singleton.getInstance(Person, 'George', 'Clooney');
console.log(person.firstname, person.lastname); // Prints George Clooney

var anotherPerson = Singleton.getInstance(Person, 'Michael', 'Jackson');
console.log(anotherPerson.firstname, anotherPerson.lastname); // Prints George Clooney

var anotherPersonMaybe = Singleton.getInstance(Person);
console.log(anotherPersonMaybe.firstname, anotherPersonMaybe.lastname); // Prints George Clooney

Simple example in single mode

function ff(d){
	this.d = d;
}

const SingletonSingle = require('js-singleton')(ff, 125);
const Singleton = require('js-singleton')();

var i1 = SingletonSingle.getInstance();
var i2 = SingletonSingle.getInstance();
var i3 = Singleton.getInstance(ff);

console.log(i1.d); // Prints 125
console.log(i2.d); // Prints 125
console.log(i3.d); // Prints 125

Example with getInstance() by passing a string alias of the function via setName()

function Complex(a, b){
  this.a = a;
  this.b = b;
}

var complex = Singleton.getInstance(Complex, 1, 2);
const SingletonSingle = require('js-singleton')(Complex);
Singleton.setName("MyCustomComplexClass", Complex);
SingletonSingle.setName("MyCustomComplexClass"); // Equivalent to previous line

var anotherComplex = Singleton.getInstance("MyCustomComplexClass");

var someOtherComplex = SingletonSingle.getInstance();

console.log(anotherComplex.a, anotherComplex.b); // Prints 1 2;
console.log(complex.a, complex.b); // Prints 1 2;
console.log(someOtherComplex.a, someOtherComplex.b); // Prints 1 2;

Example with creating multiple aliases for the same function via setName()

const Singleton = require('js-singleton')();
function Door(height, width){
  this.height = height;
  this.width = width;
}

var door = Singleton.getInstance(Door, 1.1, 2.3);
Singleton.setName("door", Door);
Singleton.setName("door", "otherDoorAlias");

var anotherDoor = Singleton.getInstance("door");

var anotherDoorMaybe = Singleton.getInstance("otherDoorAlias");

const SingletonSingle = require('js-singleton')("otherDoorAlias)";
var aDoorAlso = SingletonSingle.getInstace();

console.log(door.width, door.height); // Prints 2.3 1.1
console.log(anotherDoor.width, anotherDoor.height); // Prints 2.3 1.1
console.log(anotherDoorMaybe.width, anotherDoorMaybe.height); // Prints 2.3 1.1
console.log(aDoorAlso.width, aDoorAlso.height); // Prints 2.3 1.1

Real world example

/**
 *
 * This module is the server module (server.js)
 * 
 * @author Some Author
 *
 */

function server(options){
	// Some beautiful code
}

var options = {}; // some options

const Singleton = require('js-singleton')();
Singleton.getInstance(server, options);
// equivalent
const SingletonSingle = require('js-singleton')(server, options);

Singleton.setName("myServer", server);
// equivalent
SingletonSingle.setName("myServer");

// No need to module.export

/*
 *
 * In another file do
 *
 */
require('/path/to/server');
const Singleton = require('js-singleton')();
var myServer = Singleton.getInstance("myServer");
// equivalent
const SingletonSingle = require('js-singleton')("myServer");
var myServer = SingletonSingle.getInstance();