Run results for: Reduce with spread VS for...of with push

Run details:

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/108.0.0.0 Safari/537.36

Browser: Chrome 108

Operating system: Linux

Device Platform: Desktop

Date tested: one year ago

Test name	Executions per second
reduce with spread	71.4 Ops/sec
for...of with push	1954.5 Ops/sec

Script Preparation code:

var groups = Array.apply(null, {length: 32}).map(v => (Math.random() + 1).toString(36).substr(2))
var data = Array.apply(null, {length: 10_000}).map((v,id) => ({id, group: groups[Math.random() * groups.length | 0]}))

Tests:

reduce with spread
function groupByReduce(objectArray, property) { return objectArray.reduce((acc, obj) => { const key = obj[property]; const curGroup = acc[key] ?? []; return { ...acc, [key]: [...curGroup, obj] }; }, {}); } groupByReduce(data, 'group');
for...of with push
function groupByFor(data, keyProperty){ const groups = {} for(const entry of data){ const groupId = entry[keyProperty]; if(!groups[groupId]){ groups[groupId] = []; } groups[groupId].push(entry); } return groups; } groupByFor(data, 'group')

Run results for: Reduce with spread VS for...of with push

reduce with spread

for...of with push