Run results for: .concat() (immutable) vs .push() (mutation)

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.4.1 Safari/605.1.15

Browser: Safari 17

Operating system: Mac OS X 10.15.7

Device Platform: Desktop

Date tested: one year ago

Test name	Executions per second
concat (immutable)	64899.4 Ops/sec
push (mutability) and spread array	2411.4 Ops/sec
push (mutability) and iteration	1550.4 Ops/sec

HTML Preparation code:

<!--your preparation HTML code goes here-->

Script Preparation code:

function generateID(length = 10) {
    const characters = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
    let result = '';
    const charactersLength = characters.length;
    
    for (let i = 0; i < length; i++) {
        // Generate a random index based on characters length
        const randomIndex = Math.floor(Math.random() * charactersLength);
        // Append the character at the random index to the result string
        result += characters[randomIndex];
    }

    return result;
}

const initialArray = new Array(10000).fill('a').map(() => ({ [generateID()]: 'value' }));

const anotherArray = new Array(10000).fill('b').map(() => ({ [generateID()]: 'value' }));

Tests:

concat (immutable)
const result = initialArray.concat(anotherArray);
push (mutability) and spread array
initialArray.push(...anotherArray);
push (mutability) and iteration
anotherArray.forEach(item => initialArray.push(item));

Run results for: .concat() (immutable) vs .push() (mutation)

concat (immutable)

push (mutability) and spread array

push (mutability) and iteration