Run results for: Object.groupBy vs manual groupBy

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/136.0.0.0 Safari/537.36 Edg/136.0.0.0

Browser: Chrome 136

Operating system: Mac OS X 10.15.7

Device Platform: Desktop

Date tested: one year ago

Test name	Executions per second
Object.groupBy	5179401.0 Ops/sec
Manual groupBy	11985018.0 Ops/sec

Script Preparation code:

function groupBy(array, mapper) {
    return array.reduce(
        (acc, item) => {
            const key = mapper(item);
            const items = acc[key] ?? (acc[key] = []);
            items.push(item);
            return acc;
        }, {},
    );
}

var data = [{
        name: "John",
        age: 20,
        occupation: null,
    },
    {
        name: "Jane",
        age: 30,
        occupation: "student",
    },
    {
        name: "Jack",
        age: 40,
        occupation: "student",
    },
    {
        name: "Simon",
        age: 50,
        occupation: "student",
    },
    {
        name: "Mary",
        age: 60,
        occupation: null,
    },
    {
        name: "George",
        age: 70,
        occupation: "influencer",
    },
]

Tests:

Object.groupBy
return Object.groupBy(data, item => item.occupation)
Manual groupBy
return groupBy(data, item => item.occupation)

Run results for: Object.groupBy vs manual groupBy

Object.groupBy

Manual groupBy