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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=604790" width="100%" height="500px"></iframe>
Run details:
User agent:
Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/135.0.0.0 Safari/537.36
Browser:
Chrome 135
Operating system:
Linux
Device Platform:
Desktop
Date tested:
one year ago
Using For-In loop with type checks
41.9M/s
Using For-In loop
41.3M/s
Using the spread operator
20.2M/s
Using Object.assign
17.0M/s
View exact numbers
Test name
Executions per second
✓
Using For-In loop with type checks
41,905,448 Ops/sec
Using For-In loop
41,256,896 Ops/sec
Using the spread operator
20,164,438 Ops/sec
Using Object.assign
16,965,098 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]; } }