Run results for: for(const item of array) vs. for(const [k, v] of Object.entries(object))

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/135.0.0.0 Safari/537.36

Browser: Chrome 135

Operating system: Mac OS X 10.15.7

Device Platform: Desktop

Date tested: one year ago

for(const item of array)

107.9M/s

for(const [k, v] of Object.entries(object))

7.9M/s

View exact numbers

Test name	Executions per second
✓ for(const item of array)	107,861,376 Ops/sec
for(const [k, v] of Object.entries(object))	7,931,163 Ops/sec

Script Preparation code:

const ARRAY  = [{ key: 'a', foo: 'bar' }, { key: 'b', foo: 'bar' }, { key: 'c', foo: 'bar' }, { key: 'd', foo: 'bar' }];
const OBJECT = {'a': { foo: 'bar' }, 'b': { foo: 'bar' }, 'c': { foo: 'bar' }, 'd': { foo: 'bar' }};

Tests:

for(const item of array)
for(const item of ARRAY) { const test = true; }
for(const [k, v] of Object.entries(object))
for(const [k, v] of Object.entries(OBJECT)) { const test = true; }