Javascript sets

Set objects are collections of values. You can iterate through the elements of a set in insertion order. A value in the Setmay only occur once; it is unique in the Set's collection.

Initialize

unlike arrays sets dontt have a shortcut like square bracket for initialization we have to manually create a new instance of set class

// Arrays
const array = [];
const array = new Array()

//Sets

const set = new Set()

Add items to set

Sets are widely used for thier feature of eleminating the duplicate values
sets only contains unique items.

The values in a set can be either simple primitives like strings or integers as well as more complex object types like object literals or arrays.

const set = new Set();
set.add('Smartcodehub')
set.add(1)
set.add([1,'Neeraj'])
set.add({name:'someName'})

// if we try to add duplicate values it wont give error but the new items will not be added also 

set.add('Smartcodehub')

console.log(set.length) // 4

we can add an element at the time of initialization also

const set = new Set(['Ram', 'Raj', 'Ram', 'Ram'])

set.forEach(el=>console.log(el))

// Ram
// Raj

Use Set to ensure the uniqueness of a list of values

const array = Array
  .from(document.querySelectorAll('[id]'))
  .map(function(e) {
      return e.id
  });

const set = new Set(array);
console.assert(set.size == array.length);

Iteration on set

On top of using forEach on a set, for…of loops can also be used to iterate over sets:

const animals = new Set(['hourse','tiger','elephant','cow])

for (let animal of animals) {
  console.log(`${ animal }`);
}

Keys and Values

Sets also have the keys and values methods, with keys being an alias for values, so both methods do exactly the same thing. Using either of these methods returns a new iterator object with the values of the set in the same order in which they were added to the set. Here’s an example:

let partyItems = new Set(['🍕', '🍾', '🎊']);
let items = partyItems.values();

console.log(items.next());
console.log(items.next());
console.log(items.next());
console.log(items.next().done);

// Object {
//   done: false,
//   value: "🍕"
// }

// Object {
//   done: false,
//   value: "🍾"
// }

// Object {
//   done: false,
//   value: "🎊"
// }

// true

Remove duplicate elements from the array

this is a very common question asked in interviews. we can use Sets to solve this

const duplicates = [1, 3, 4, 2, 1, 2, 3, 8];
const unique = [...new Set([...duplicates])]
console.log(unique)

Originally published at https://blog.smartcodehub.com on February 15, 2021.