ES6: Sets and WeakSets

Set

A set is a unique array whose properties you can set only once.

You can’t access the items individually,

and it is not index based.

It is a list of items which we can add to, remove from and loop over

const people = new Set();

people.add(‘AK’);

people.add(‘BK’);

people.add(‘CK’);

>people.size

gives the length of the set

>people.delete(‘BK’);

deletes the item from the set without needing an index

>people.clear();

empties the set

>people.values();

We get a setIterator, which we can .next() over

const it = people.values();

it.next()

it.next()

You can also set a for of loop

for (const person of people){

console.log(person);

}

Declaring a set

1.Normal array like declaration

const students = new Set([‘AK’,’BK’,’CK’]);

2.Convert to set from an existing array

const dogs = [‘Woofer’,’Bowwower’];

const dogSet = new Set(dogs);

.has property

students.has(‘AK’);

-true

Set properties:

add

delete

clear

size

values

Example

Imagine you offer brunch in your restaurant and there is a line for it.

You can handle the line using Set.

const brunch = new Set();

brunch.add(‘AK’);

brunch.add(‘KB’)’

const line = brunch.values();

console.log(line.next().value); //line.next gives us the generator and .value gives us the value

When you call next on a Set, the item removes itself from the Set

You can still add people to the Set after using next

Weak Set

WeakSets can only contain an object type.

You can’t loop over it

There is no .clear() method

WeakSets clean themselves up. When the reference to an item is deleted, it garbage collects automatically

const weakSauce = new WeakSet([dog1, dog2]);

dog1 = null; //dog1 disappears after a few seconds automatically