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Run results for:
JavaScript Array Copy 3
Testing the results for the fastest approach of shallow copying an array in JavaScript (concat, slice, for loop, and while loop).
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<iframe src="https://measurethat.net/Embed?id=617246" 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/139.0.0.0 Safari/537.36
Browser:
Chrome 139
Operating system:
Mac OS X 10.15.7
Device Platform:
Desktop
Date tested:
10 months ago
Array.slice
2.2M/s
Array.concat
2.1M/s
For loop no push, prefill
307K/s
For loop no push
303K/s
View exact numbers
Test name
Executions per second
✓
Array.slice
2,229,123 Ops/sec
Array.concat
2,108,258 Ops/sec
For loop no push, prefill
306,778 Ops/sec
For loop no push
302,819 Ops/sec
Script Preparation code:
var arrayToCopy = new Array(1000).fill(5); var shallowCopy = [];
Tests:
Array.concat
shallowCopy = arrayToCopy.concat();
Array.slice
shallowCopy = arrayToCopy.slice();
For loop no push
var arrayLength = arrayToCopy.length; shallowCopy.length = arrayLength; for (let i = 0; i < arrayLength; ++i) { shallowCopy[i] = arrayToCopy[i]; }
For loop no push, prefill
var arrayLength = arrayToCopy.length; for (let i = 0; i < arrayLength; ++i) { shallowCopy[i] = arrayToCopy[i]; }