JavaScript WeakMap

JavaScript WeakMap is a built-in object that represents a collection of key-value pairs in which the keys are weakly referenced. This means that if there are no other references to a key in your code, the key and its corresponding value can be garbage collected.

Unlike Map, WeakMap keys must be objects, and the keys are not enumerable, meaning you can’t iterate over the keys using methods like forEach or for...of.

Here’s an example of how to use WeakMap:

// Create a WeakMap
const myWeakMap = new WeakMap();

// Create an object as a key
const key = {};

// Set a value in the WeakMap using the key
myWeakMap.set(key, 'Value');

// Get the value associated with the key
const value = myWeakMap.get(key);
console.log(value); // Output: Value

// Check if the key exists in the WeakMap
const hasKey = myWeakMap.has(key);
console.log(hasKey); // Output: true

// Delete the key-value pair from the WeakMap
myWeakMap.delete(key);

// Check if the key still exists
const hasKeyAfterDeletion = myWeakMap.has(key);
console.log(hasKeyAfterDeletion); // Output: false

In the above example, we create a WeakMap called myWeakMap. We create an object key and use it as the key to set a value in the WeakMap. We can then retrieve the value using get(), check if the key exists using has(), and delete the key-value pair using delete().

One important thing to note is that because the keys in WeakMap are weakly referenced, they cannot be used for iterating over the WeakMap or obtaining the size of the WeakMap. WeakMap is primarily useful in scenarios where you need to associate additional data with existing objects without affecting their normal garbage collection behavior.