Sets

Sets were introduced as part of the ES2015 specification. As described by MDN they:

let you store unique values of any type, whether primitive values or object references.

They are similar to arrays but as described above the values must be unique duplicates are not allowed.

They can be initialised through the constructor or with an array of values e.g.

const mySet = new Set()

const mySet2 = new Set(['hello', 'world', 2021])

There are a number of methods you can use depending on what you are trying to achieve e.g. size to get the number of values

mySet2.size // 3

To add and remove values you use the use and delete methods respectively e.g.

mySet2.add(4) // ['hello', 'world', 2021, 4 ]

mySet2.delete(2021) // ['hello', 'world', 4 ]

If you wish to remove all the values from a Set, use the clear method e.g.

mySet2.clear() // Set []

You can iterate/loop through a Set using forEach or a for...of loop e.g.

for(let [key, value] of mySet){
  // do something
}

mySet.forEach( (val) => {
  console.log(val)
}

To check if an element is present in a Set use the has method which will return a Boolean e.g.

mySet.has('hello') // true

mySet.has(2021) // false

The values and entries methods

You convert to an array if needed e.g.

Array.from(mySet) // Array: ['hello', 'world', 4]