Run results for: Plain object, for vs for in vs for of vs while

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/101.0.4951.64 Safari/537.36

Browser: Chrome 101

Operating system: Mac OS X 10.15.7

Device Platform: Desktop

Date tested: one year ago

Test name	Executions per second
for loop	1315346.0 Ops/sec
for of	1350934.0 Ops/sec
for in	1834923.0 Ops/sec
while	1898109.0 Ops/sec

Script Preparation code:

var a = {
    first: 'john',
    last: 'smith',
    address: {
        street: 'street street'
    }
};

var b = {
    first: 'j',
    last: 's'
};

Tests:

for loop
const props = Object.keys(a); const length = props.length; let hasNewKey = false; for (let i = 0; i < length; i++) { const key = props[i]; if (!(key in b)) { hasNewkey = true; } }
for of
const props = Object.keys(a); let hasNewKey = false; for (const key of props) { if (!(key in b)) { hasNewkey = true; } }
for in
let hasNewKey = false; for (const key in a) { if (!(key in b)) { hasNewkey = true; } }
while
let hasNewKey = false; const props = Object.keys(a); let key, i = 0; while (key = props[i++]) { if (!(key in b)) { hasNewKey = true; } }

Run results for: Plain object, for vs for in vs for of vs while

compare different ways to loop the keys of an object

for loop

for of

for in

while