What happens to an ES6-Promise when you no longer hold a reference to it?

Question

Background

You can see from the following code:

var foo1 = new Promise (function (resolve, reject){};

var foo2 = new Promise (function (resolve, reject) {

    resolve('succes!');
});

var foo3 = new Promise (function (resolve, reject) {

    reject(Error('Failure!'));
});

console.log (typeof foo1 === 'object'); // true
console.log (Object.getOwnPropertyNames(foo1)); // []
console.log (foo1.length); // undefined

console.log (foo1); // Promise { <pending> }
console.log (foo2); // Promise { 'succes!' }
console.log (foo3); // Promise { <rejected> [Error: Failure!] }

that the variable referencing a Promise is referencing a special Promise object containing either the state or the outcome of the function you pass to the Promise constructor. If you then set:

foo1 = null;
foo2 = null;
foo3 = null;

you are no longer able to access this state or outcome.

Question

Does a Promise get garbage-collected in the above situation and if no, does that not create a risk of causing memory leaks?

Answer 1

Does a Promise get garbage-collected in the above situation?

Yes. A promise object is just like every other object in that regard.

Some implementations (Firefox) do have special behaviour where unhandled-rejection detection depends on garbage collection, but that doesn't really change anything about the promise object being collected.