Map-vs-native-cache.js

/*
❯ node -v
v14.15.1

❯ node Map-vs-native-cache.js
Testing caching
Map x 57.19 ops/sec ±1.83% (59 runs sampled)
Native x 50.16 ops/sec ±2.87% (63 runs sampled)
Fastest is Map
*/

var Benchmark = require('benchmark');
var suite = new Benchmark.Suite;

var testArray = [];

for (var s = 0; s < 100000; s++) {
    testArray.push(Math.random().toString(36).slice(2));
}

console.log('Testing caching')
suite
    .add('Map', () => objectMap(testArray))
    .add('Native', () => objectNative(testArray))
    .on('cycle', event => console.log(String(event.target)))
    .on('complete', function() {console.log('Fastest is ' + this.filter('fastest').map('name'))})
    .run({ 'async': true });


function objectMap(arr) {
    var result = [];
    var cache = new Map();

    for(var i = 0; i < arr.length; i++) {
        var item = arr[i];

        if(cache.has(item)) {
            result.push(cache.get(item));
        } else {
            cache.set(item, item);
            result.push(item);
        }
    }

    return result;
}

function objectNative(arr) {
    var result = [];
    var cache = Object.create(null);

    for(var i = 0; i < arr.length; i++) {
        var item = arr[i];

        if(item in cache) {
            result.push(cache[item]);
        } else {
            cache[item] = item;
            result.push(item);
        }
    }

    return result;
}

This benchmark does not show the whole story. Your key is just a number. Map is designed for strings keys.

Here is the better benchmark
https://jsbench.me/h1kje2tt1b

@aminya Thank you. I updated the code