Benchmark: JavaScript Array Copy

JavaScript Array Copy (version: 0)

Testing the results for the fastest approach of shallow copying an array in JavaScript (concat, slice, for loop, and while loop).

Comparing performance of: `Array.concat vs Array.slice vs For loop vs For loop with declared length vs While loop vs Spread operator vs Slice with begin argument vs Slice with begin and end argument`

Created: 4 years ago by: Guest

Go to the latest result

Script Preparation code:

var arrayToCopy = [ "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello" ];
var shallowCopy = [];

Tests:

Array.concat
shallowCopy = arrayToCopy.concat();
Array.slice
shallowCopy = arrayToCopy.slice();
For loop
for (let i = 0; i < arrayToCopy.length; ++i) { shallowCopy.push(arrayToCopy[i]); }
For loop with declared length
var arrayLength = arrayToCopy.length; for (let i = 0; i < arrayLength; ++i) { shallowCopy.push(arrayToCopy[i]); }
While loop
let i = arrayToCopy.length - 1; while (i--) { shallowCopy.push(arrayToCopy[i]); }
Spread operator
shallowCopy = [...arrayToCopy];
Slice with begin argument
shallowCopy = arrayToCopy.slice(0);
Slice with begin and end argument
shallowCopy = arrayToCopy.slice(0, arrayToCopy.length);

Historical Performance Data aggregated from 10 community runs

Desktop Results:

Chrome 10 runs

Slice with begin argument

3.8M/s

Spread operator

3.6M/s

Array.slice

3.6M/s

Array.concat

3.4M/s

Slice with begin and end argument

2.5M/s

While loop

154K/s

For loop with declared length

149K/s

For loop

102K/s

Fastest: Slice with begin argument (37.0x faster)

View exact numbers

✓ Slice with begin argument: 3,766,500 ops/sec
• Spread operator: 3,627,908 ops/sec
• Array.slice: 3,589,992 ops/sec
• Array.concat: 3,428,044 ops/sec
• Slice with begin and end argument: 2,450,696 ops/sec
• While loop: 154,476 ops/sec
• For loop with declared length: 148,564 ops/sec
• For loop: 101,931 ops/sec

Results show median performance across all community submissions. Run this benchmark yourself to verify on your device.

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array.concat
Array.slice
For loop
For loop with declared length
While loop
Spread operator
Slice with begin argument
Slice with begin and end argument

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36

Browser/OS: Chrome 131 on Windows

View result in a separate tab

Slice with begin argument

3.4M/s

Spread operator

3.3M/s

Array.concat

3.3M/s

Array.slice

3.3M/s

Slice with begin and end argument

2.2M/s

While loop

138K/s

For loop with declared length

130K/s

For loop

93K/s

View exact numbers

Test name	Executions per second
✓ Slice with begin argument	3,431,886 Ops/sec
Spread operator	3,327,696 Ops/sec
Array.concat	3,315,430 Ops/sec
Array.slice	3,300,158 Ops/sec
Slice with begin and end argument	2,225,193 Ops/sec
While loop	138,394 Ops/sec
For loop with declared length	129,563 Ops/sec
For loop	92,926 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

LLMs can make mistakes. Check important info.

The provided JSON represents a JavaScript benchmark test case on MeasureThat.net, designed to compare the performance of different methods for shallow copying an array in JavaScript.

**Methods being compared:**

1. `Array.concat()`
2. `Array.slice()`
3. `For loop` with and without declared length
4. `While loop`
5. Spread operator (`[...]`)
6. `Array.slice()` with begin argument

**Pros and cons of each approach:**

1. **Array.concat():**
	* Pros: Simple, easy to implement.
	* Cons: Creates a new array object, which can lead to performance issues for large arrays.
2. **Array.slice():**
	* Pros: Fast, efficient way to create a shallow copy of an array.
	* Cons: May not be suitable for large arrays due to memory constraints.
3. **For loop with declared length:**
	* Pros: Can be more efficient than `Array.slice()` when dealing with large arrays.
	* Cons: Requires manual management of the loop counter and array indexing, which can add complexity.
4. **While loop:**
	* Pros: Similar to the for loop approach but uses a different looping mechanism.
	* Cons: May not be as straightforward or efficient as other methods.
5. **Spread operator (`[...]`):**
	* Pros: Simple, modern way to create a shallow copy of an array.
	* Cons: Only supported in ECMAScript 2018 and later.
6. **Array.slice() with begin argument:**
	* Pros: Allows for more control over the slice operation, which can be beneficial when working with specific array segments.

**Other considerations:**

* The benchmark results are influenced by factors such as JavaScript engine implementation, browser version, operating system, and hardware.
* The performance differences between methods may vary depending on the specific use case or scenario.
* Some methods, like `Array.slice()` with begin argument, offer more flexibility but may require additional setup.

**Libraries used:**

None mentioned in the provided JSON. However, some libraries might be used for testing purposes (e.g., benchmarking libraries).

**Special JavaScript features/syntax:**

None explicitly mentioned in the provided JSON.

JavaScript Array Copy (version: 0)

Testing the results for the fastest approach of shallow copying an array in JavaScript (concat, slice, for loop, and while loop).

Comparing performance of: Array.concat vs Array.slice vs For loop vs For loop with declared length vs While loop vs Spread operator vs Slice with begin argument vs Slice with begin and end argument

Created: 4 years ago by: Guest

Go to the latest result

Array.concat

Array.slice

For loop

For loop with declared length

While loop

Spread operator

Slice with begin argument

Slice with begin and end argument

Historical Performance Data aggregated from 10 community runs

Desktop Results:

Chrome 10 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

Related benchmarks

Comparing performance of: `Array.concat vs Array.slice vs For loop vs For loop with declared length vs While loop vs Spread operator vs Slice with begin argument vs Slice with begin and end argument`