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Run results for:
JavaScript spread operator vs Object.assign vs only-null-checked for-in loop performance
Measure the fastest way to merge objects, without mutation.
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<iframe src="https://measurethat.net/Embed?id=619478" width="100%" height="500px"></iframe>
Run details:
User agent:
Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/141.0.0.0 Safari/537.36
Browser:
Chrome 141
Operating system:
Mac OS X 10.15.7
Device Platform:
Desktop
Date tested:
9 months ago
Using For-In loop with type checks
64.5M/s
Using For-In loop
64.1M/s
Using the spread operator
34.0M/s
Using Object.assign
26.6M/s
View exact numbers
Test name
Executions per second
✓
Using For-In loop with type checks
64,490,060 Ops/sec
Using For-In loop
64,082,452 Ops/sec
Using the spread operator
33,980,480 Ops/sec
Using Object.assign
26,552,656 Ops/sec
Tests:
Using the spread operator
const firstObject = { sampleData: 'Hello world' } const secondObject = { moreData: 'foo bar' } const finalObject = { ...firstObject, ...secondObject };
Using Object.assign
const firstObject = { sampleData: 'Hello world' } const secondObject = { moreData: 'foo bar' } const finalObject = Object.assign({}, firstObject, secondObject);
Using For-In loop
const firstObject = { sampleData: 'Hello world' } const secondObject = { moreData: 'foo bar' } const finalObject = {} for (let key in firstObject) { finalObject[key] = firstObject[key]; } for (let key in secondObject) { finalObject[key] = secondObject[key]; }
Using For-In loop with type checks
const firstObject = { sampleData: 'Hello world' } const secondObject = { moreData: 'foo bar' } const finalObject = {} if (firstObject != null) { for (let key in firstObject) { finalObject[key] = firstObject[key]; } } if (secondObject != null) { for (let key in secondObject) { finalObject[key] = secondObject[key]; } }