Run results for: Map vs Two Arrays

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/85.0.4183.121 Safari/537.36

Browser: Chrome 85

Operating system: Windows

Device Platform: Desktop

Date tested: 4 years ago

Test name	Executions per second
Map (delete)	3724.0 Ops/sec
Two Arrays	210.0 Ops/sec
Map (set false)	4764.2 Ops/sec

Script Preparation code:

const size = 3000
var input = new Array(size).fill().map(() => Math.round(size / 3 * Math.random()))

function getPairCount() {
    const pairMap = new Map()
    let pairs = 0
    input.forEach((number) => {
        if (!pairMap.has(number)) pairMap.set(number, true)
        else {
            pairMap.delete(number)
            pairs++
        }
    })
    return pairs;
}

function countPairs() {
    let nums = [];
    let count = [];
    input.forEach((num) => {
        if (!nums.includes(num)) {
            nums.push(num);
            count.push(0);
        }
        count[nums.indexOf(num)] += 1;
    });
    let pairs = 0;
    count.forEach((num) => {
        pairs += Math.floor(num / 2);
    })
    return pairs;
}

function findPairs() {
    const map = new Map()
    let pairs = 0
    input.forEach(num => {
        if (map.get(num)) {
            pairs += 1
            map.set(num, false)
        } else map.set(num, true)
    })
    return pairs
}

Tests:

Map (delete)
getPairCount()
Two Arrays
countPairs()
Map (set false)
findPairs()

Run results for: Map vs Two Arrays

Map (delete)

Two Arrays

Map (set false)