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Run results for:
JavaScript spread operator vs Object.assign vs for-in loop safe performance
Measure the fastest way to merge objects, without mutation.
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<iframe src="https://measurethat.net/Embed?id=529126" width="100%" height="500px"></iframe>
Run details:
User agent:
Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.3 Safari/605.1.15
Browser:
Safari 17
Operating system:
Mac OS X 10.15.7
Device Platform:
Desktop
Date tested:
2 years ago
Using For-In loop
42.0M/s
Using the spread operator
16.6M/s
Using Object.assign
12.5M/s
Using For-In loop with hasOwnProperty
2.4M/s
View exact numbers
Test name
Executions per second
✓
Using For-In loop
41,968,252 Ops/sec
Using the spread operator
16,598,274 Ops/sec
Using Object.assign
12,480,818 Ops/sec
Using For-In loop with hasOwnProperty
2,409,474 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 hasOwnProperty
const firstObject = { sampleData: 'Hello world' } const secondObject = { moreData: 'foo bar' } const finalObject = {} for (let key in firstObject) { if (Object.prototype.hasOwnProperty.call(firstObject, key)) { finalObject[key] = firstObject[key]; } } for (let key in secondObject) { if (Object.prototype.hasOwnProperty.call(secondObject, key)) { finalObject[key] = secondObject[key]; } }