Node 18, chai assertions, instanceof checks, sample tests and better initial code (author gone)

Node v12 should be used along with its appropiate assertion tools (Mocha + Chai).
Refer to this and this

No random tests

No sample tests

You could add sample tests

var obj1 = new Singleton();
var obj2 = new Singleton();

obj1.test = 1;

Test.assertEquals(obj2, obj1);
Test.assertEquals(obj2.test, obj1.test);
Test.expect(obj1 instanceof Singleton);

hi, just wondering if no error detected for the code should it pass or not? because it is not passing eventhough (obj1 === obj2) is true and obj2.test is = 1.

thanks

Sam

I guess all of the instances should point to the same location in memory, so probably this solution would make more sense.
This the Singleton pattern is from "JavaScript Patterns" by Stoyan Stefanov.

var Singleton = function() {
    var instance;
    Singleton = function() {
        return instance;
    };
    Singleton.prototype = this;
    instance = new Singleton();
    instance.constructor = Singleton;
    instance.test = 1;
    return Singleton;
};

The instance variable for the Singleton should be private; no public properties except those inherited from Object.

I also agree very strongly with spicydonuts that the returned instance should pass var obj = new Singleton();Test.expect(obj instanceof Singleton)