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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=594390" width="100%" height="500px"></iframe>
Run details:
User agent:
Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/135.0.0.0 Safari/537.36
Browser:
Chrome 135
Operating system:
Windows
Device Platform:
Desktop
Date tested:
one year ago
Using For-In loop
32.6M/s
Using the spread operator
13.9M/s
Using For-In loop with hasOwnProperty
13.2M/s
Using Object.assign
12.5M/s
View exact numbers
Test name
Executions per second
✓
Using For-In loop
32,594,164 Ops/sec
Using the spread operator
13,923,456 Ops/sec
Using For-In loop with hasOwnProperty
13,156,926 Ops/sec
Using Object.assign
12,456,927 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]; } }