Benchmark: Concat vs Slice - MeasureThat.net

Tests:

Array.prototype.slice
var other = [ 1, 2 ].slice();
Array.prototype.concat
var other = [].concat([ 1, 2 ]);

Historical Performance Data aggregated from 9 community runs

Desktop Results:

Chrome 9 runs

Array.prototype.slice

104.6M/s

Array.prototype.concat

70.6M/s

Fastest: Array.prototype.slice (1.5x faster)

View exact numbers

✓ Array.prototype.slice: 104,606,432 ops/sec
• Array.prototype.concat: 70,593,360 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.prototype.slice
Array.prototype.concat

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/136.0.0.0 Safari/537.36

Browser/OS: Chrome 136 on Windows

View result in a separate tab

Array.prototype.slice

108.1M/s

Array.prototype.concat

79.2M/s

View exact numbers

Test name	Executions per second
✓ Array.prototype.slice	108,074,640 Ops/sec
Array.prototype.concat	79,243,296 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what's being tested.

**What is tested?**

The provided JSON defines two test cases for comparing the performance of `Array.prototype.slice()` and `Array.prototype.concat()`. These are two methods used to manipulate arrays in JavaScript.

**Options compared:**

The main difference between `slice()` and `concat()` lies in how they handle array modifications:

1. **`Array.prototype.slice()`**: Returns a shallow copy of the specified portion of an array. This method modifies the original array by shifting its elements.
2. **`Array.prototype.concat()`**: Returns a new array that is the concatenation of two or more arrays.

**Pros and cons:**

* `slice()`: Pros:
	+ More efficient, as it doesn't create a new array.
	+ Can be used for in-place modifications.
* Cons:
	+ Modifies the original array, which can lead to unexpected behavior if not handled carefully.
	+ Returns a shallow copy, which means that any changes made to the returned array will affect the original array.
* `concat()`: Pros:
	+ Creates a new array, which is generally safer and more predictable.
	+ Does not modify the original arrays.
* Cons:
	+ Less efficient than `slice()` for large arrays.
	+ Can be slower due to the overhead of creating a new array.

**Other considerations:**

Both methods have their use cases:

* Use `slice()` when you need to manipulate an array in-place or need to create a shallow copy.
* Use `concat()` when you want to ensure that your code is predictable and doesn't modify the original arrays.

**Library usage:**

There are no libraries used in these test cases.

**Special JS features/syntax:**

There are no special JavaScript features or syntax used in these test cases. The focus is on comparing the performance of `slice()` and `concat()` methods.

**Other alternatives:**

If you want to compare the performance of other array manipulation methods, such as:

* Using `Array.prototype.map()`, `Array.prototype.filter()`, or `Array.prototype.reduce()` instead of `slice()` or `concat()`.
* Comparing the performance of different data structures, like arrays versus linked lists.
* Examining the performance impact of using modern JavaScript features like `let` and `const` declarations.

You would need to create new benchmark test cases for these scenarios.

Concat vs Slice (version: 0)

Comparing performance of: `Array.prototype.slice vs Array.prototype.concat`

Created: 7 years ago by: Guest

Go to the latest result

Array.prototype.slice

Array.prototype.concat

Historical Performance Data aggregated from 9 community runs

Desktop Results:

Chrome 9 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

Concat vs Slice (version: 0)

Comparing performance of: Array.prototype.slice vs Array.prototype.concat

Created: 7 years ago by: Guest

Go to the latest result

Array.prototype.slice

Array.prototype.concat

Historical Performance Data aggregated from 9 community runs

Desktop Results:

Chrome 9 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

Comparing performance of: `Array.prototype.slice vs Array.prototype.concat`