Run results for: Array flatten implementations [high volume]

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:146.0) Gecko/20100101 Firefox/146.0

Browser: Firefox 146

Operating system: Windows

Device Platform: Desktop

Date tested: 9 months ago

Benchmark engine: Benchmark.js

Manual copy by index #2

3K/s

Manual copy with push

3K/s

Manual copy by index #1

2K/s

flat

2K/s

reduce + concat

194/s

reduce + spread

36/s

View exact numbers

Test name	Executions per second
✓ Manual copy by index #2	2,924 Ops/sec
Manual copy with push	2,727 Ops/sec
Manual copy by index #1	2,352 Ops/sec
flat	1,743 Ops/sec
reduce + concat	194 Ops/sec
reduce + spread	36 Ops/sec

Script Preparation code:

var params = [];
for (let i = 0; i < 100; i++) {
    const arr = [];
    for (let j = 0; j < 1000; j++) {
        arr.push(999 * Math.random());
    }
    params.push(arr);
}

function getTotal(arr) {
    let total = 0;
    for (let i = 0; i < arr.length; i++) {
        total += arr[i].length;
    }
    return total;
}

Tests:

reduce + concat
return params.reduce((acc, val) => acc.concat(val), []);
flat
return params.flat();
Manual copy by index #1
const result = new Array(getTotal(params)); for (let i = 0; i < params.length; i++) { for (let j = 0; j < params[i].length; j++) { result[params[i].length * i + j] = params[i][j]; } } return result;
Manual copy by index #2
const result = new Array(getTotal(params)); for (let i = 0, k = 0; i < params.length; i++) { const arr = params[i]; for (let j = 0; j < arr.length; j++) { result[k] = arr[j]; k++; } } return result;
Manual copy with push
const result = []; for (let i = 0; i < params.length; i++) { const arr = params[i]; for (let j = 0; j < arr.length; j++) { result.push(arr[j]); } } return result;
reduce + spread
return params.reduce((acc, val) => [...acc, ...val], []);