Run results for: Map vs forEach

Run details:

User agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:49.0) Gecko/20100101 Firefox/49.0

Browser: Firefox 49

Operating system: Windows 7

Device Platform: Other

Date tested: 8 years ago

Test name	Executions per second
Map	7047.6 Ops/sec
forEach	8205.2 Ops/sec

Tests:

Map
const createLists = (arr = []) => [ ...arr.reduce((map, val) => { if (!map.has(val)) { map.set(val, [val]); } else { map.get(val).push(val); } return map; }, new Map()).values() ]; console.log(createLists([1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 4, 4, 4, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 0, 0, 0, 0, 0]));
forEach
function createLists(arr = []) { let authors = []; let list = []; arr.forEach(item => { let authorIndex = authors.includes(item) ? authors.indexOf(item) : (authors.push(item) - 1); list[authorIndex] = list[authorIndex] || []; list[authorIndex].push(item); }); return list; } console.log(createLists([1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 4, 4, 4, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 0, 0, 0, 0, 0]));