Run results for: POJO hash table vs Map

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/83.0.4103.116 Safari/537.36

Browser: Chrome 83

Operating system: Windows

Device Platform: Desktop

Date tested: 4 years ago

Test name	Executions per second
POJO - for...in	7432.6 Ops/sec
POJO - for...of Object.entries	11571.3 Ops/sec
POJO - reduce Object.entries	11907.5 Ops/sec
Map - forEach	18654.6 Ops/sec
Map - for...of entries	22602.1 Ops/sec

Script Preparation code:

var pojo1 = {};
var pojo2 = {};

var map1 = new Map();
var map2 = new Map();

for (var i = 0; i < 300; i++) {
    var val1 = Math.round(Math.random() * 10);
    var val2 = Math.round(Math.random() * 10);

    pojo1[`${i}`] = val1;
    map1.set(`${i}`, val1);

    pojo2[`${i}`] = val2;
    map2.set(`${i}`, val2);
}

Tests:

POJO - for...in
var diff = []; for (var key in pojo1) { if (pojo1.hasOwnProperty(key)) { if (pojo1[key] !== pojo2[key]) { diff.push(key); } } }
POJO - for...of Object.entries
var diff = []; for (var [key, val] of Object.entries(pojo1)) { if (val !== pojo2[key]) { diff.push(key); } }
POJO - reduce Object.entries
var diff = Object.entries(pojo1).reduce((acc, [key, val]) => { if (val !== pojo2[key]) { acc.push(key); } return acc; }, []);
Map - forEach
var diff = []; map1.forEach((val, key) => { if (val !== map2.get(key)) { diff.push(key); } });
Map - for...of entries
var diff = []; for (var [key, val] of map1.entries()) { if (val !== map2.get(key)) { diff.push(key); } }

Run results for: POJO hash table vs Map

Benchmark of various iteration and diffing strategies over a plain JavaScript-object-as-hash-table vs the ES6 Map data structure

POJO - for...in

POJO - for...of Object.entries

POJO - reduce Object.entries

Map - forEach

Map - for...of entries