Introduction to E2015 Set Objects

Introduction

Set objects are constructed using new Set().

Set object

A set is a “set of " unique values. Say you have a simple game and need to track the position of mouse clicks. You’d store every position in a set object. Duplicate values are discarded when an attempt to add the set object is made.

Sample code showing a simple Set object usage:

function main() {

    const gameScreen = document.getElementById('game-screen')
    gameScreen.addEventListener('click' updateAction)

    const cursorPositions = new Set()
    function updateAction(event) {
      let position = {x: e.clientX, y: e.clientY}
      cursorPositions.add(position) // any duplicate values are discarded, which is ideal in this case
    }
    // use unique cursorPositions below
}

while(true) {
  main()
}

Duplicate values are discarded when added to a set. This is useful for capturing and storing unique values where duplicate values are not needed.

const letters = new Set()
letters.add('A')
letters.add('B')
letters.add('A') // duplicate entry is ignored
console.log(letters) // Set {2} {'A', 'B'} 

Summary

1. The set object provides a way of storing data where duplicate values are not required.

Note: Most languages including JavaScript offer a lot of language features but it’s not a good approach to try learning all these language features at a go. However, knowing they exist is enough as it helps one know where to look when the need arises.