Run results for: forEach vs reduce vs for - fill object spread

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/80.0.3987.162 Safari/537.36

Browser: Chrome 80

Operating system: Mac OS X 10.12.6

Device Platform: Desktop

Date tested: 4 years ago

Script Preparation code:

var arr = [];
for (var i = 0; i < 50000; i++) {
  arr.push(i);
}

Tests:

map then forEach with spread
var objSpread = {}; var mapped = arr.map(item => ({ [item]: { exists: true }})); mapped.forEach(item => { objSpread = { ...objSpread, ...item }; });
reduce spread
var objReduce = arr.reduce((acc, item) => { var temp = { [item]: { exists: true } }; return {...acc, ...temp }; }, {});
map then forEach with assign
var objAssign = {}; var mapped = arr.map(item => ({ [item]: { exists: true }})); mapped.forEach(item => { var key = Object.keys(item)[0]; objAssign[key] = item[key] });
reduce assign
var objReduce = arr.reduce((acc, item) => { var temp = { [item]: { exists: true } }; var key = Object.keys(temp)[0]; acc[key] = temp[key]; return acc; }, {});