Run results for: Spread vs mutating

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/86.0.4240.111 Safari/537.36

Browser: Chrome 86

Operating system: Mac OS X 10.15.6

Device Platform: Desktop

Date tested: 3 years ago

Script Preparation code:

var array = Array.from(Array(1000).keys());

Tests:

Spread operator
array.reduce((acc, number) => ({ ...acc, [number]: null }), {});
Mutate accumulator
array.reduce((acc, number) => { acc[number] = null; return acc; }, {});
Object.assign
array.reduce((acc, number) => (Object.assign({}, acc, { [number]: null })))