WeakSet in JavaScript. Code examples

This method is similar to the usual Set. It can also only store unique values, but each element must represent an object.

Let’s create a WeakSet object:

    const weakSet = new WeakSet();

Let’s create a WeakSet object with initial parameters:

    const weakSet = new WeakSet([{ name: "Alexander", age: 33 }, { name: "Timote", age: 25 }]);

To add data to a WeakSet, use the add method:

    const weakSet = new WeakSet();
    weakSet.add({ lang: "English" });

For deletion, the delete() method is used, into which a reference to the object to be deleted is passed:

    const weakSet = new WeakSet();
    const js = { lang: "JavaScript" };
    weakSet.add(js);

    weakSet.delete(js);

The has method allows you to check if an object is in the WeakSet:

    const js = { lang: "JavaScript" };
    const ts = { lang: "TypeScript" };
    const weakSet = new WeakSet([js, ts]);
    console.log(weakSet.has(ts));       // true

Objects are passed to WeakSet by reference. And when an object ceases to exist for various reasons, it is removed from the WeakSet. So, consider the following example:

    let js = { lang: "JavaScript" };
    let ts = { lang: "TypeScript" };
    
	const weakSet = new WeakSet([js, ts]);

    js = null;

    const timerId = setTimeout(function () {
        console.log(weakSet);   // {{lang: "TypeScript"}}
        clearTimeout(timerId);
    }, 9000);