Run results for: [{key, fn}, ...] vs {[key]: fn, ...}

Run details:

User agent: Mozilla/5.0 (Windows NT 6.3; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/90.0.4430.93 Safari/537.36

Browser: Chrome 90

Operating system: Windows 8.1

Device Platform: Desktop

Date tested: 3 years ago

Test name	Executions per second
Array	1.8 Ops/sec
Object	1.3 Ops/sec
Reflect.ownKeys	0.9 Ops/sec

Script Preparation code:

var data = {};
var array = [];
var object = {};
for (var i = 0; i < 1000000; i++) {
  var key = Math.random().toString(16).slice(2, 10);
  var fn = function(k) {return data[k];}
  data[key] = Math.random();
  array.push({
    key: key,
    fn: fn
  });
  object[key] = fn;
}

Tests:

Array
var sum = 0; for (var i = 0; i < array.length; i++) { var item = array[i]; sum += item.fn(item.key); } sum;
Object
var sum = 0; var keys = Object.keys(object); for (var i = 0; i < keys.length; i++) { sum += object[key](keys[i]); } sum;
Reflect.ownKeys
var sum = 0; var keys = Reflect.ownKeys(object); for (var i = 0; i < keys.length; i++) { sum += object[key](keys[i]); } sum;

Run results for: [{key, fn}, ...] vs {[key]: fn, ...}

Iterating over array of {key, fn} vs object of {[key]: fn}

Array

Object

Reflect.ownKeys