Benchmark: Array slice vs for loop (set by index)

Script Preparation code:

var data = [1, 2, 3, 4, 5, 6, 7, 8, 9, 0];

Tests:

slice
var copy = data.slice(3, 8);
push
var copy = []; for (var i = 3; i < 8; i++) { copy[i] = data[i]; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
slice
push

Fastest: N/A

Slowest: N/A

Autogenerated LLM Sumamry (model llama3.1:latest, generated 4 days ago):

LLMs can make mistakes. Check important info.

Let's dive into the explanation.

**What is being tested?**

The benchmark compares two different ways of copying an array in JavaScript: using the `slice()` method and using a traditional `for` loop with push operations.

**Test Case 1: Using slice()**

* **Benchmark Definition**: `var copy = data.slice(3, 8);`
* **Library/Feature**: None
* **Description**: This test case uses the `slice()` method to create a new array (`copy`) that contains elements from index 3 to index 7 of the original array (`data`).
	+ **Pros**: The `slice()` method is concise and easy to read.
	+ **Cons**: Creating an entirely new array can be memory-intensive for large datasets.

**Test Case 2: Using a traditional for loop**

* **Benchmark Definition**: `var copy = []; for (var i = 3; i < 8; i++) { copy[i] = data[i]; }`
* **Library/Feature**: None
* **Description**: This test case uses a traditional `for` loop to iterate over the elements of the original array (`data`) and push them into a new array (`copy`), starting from index 3 to index 7.
	+ **Pros**: The `push()` method can be more memory-efficient than creating an entirely new array, especially for large datasets.
	+ **Cons**: This approach is less concise than using the `slice()` method and may be harder to read.

**Other alternatives?**

Yes! There are other ways to copy arrays in JavaScript. Some options include:

* Using the spread operator (`[...data]`, `[...data.slice(3, 8)]`): Creates a new array with all elements of the original array or a subset thereof.
* Using `Array.from()` (ES6+): Converts an iterable into an array.

Keep in mind that these alternatives might have their own performance implications and use cases.

**What do the results mean?**

The latest benchmark result shows that using the `slice()` method (`TestName`: "slice") is significantly faster than using a traditional `for` loop with push operations (`TestName`: "push") on this particular device platform (Chrome Mobile 117, Android). The execution speed per second is approximately 4-5 times higher for the `slice()` method.

However, it's essential to note that performance results can vary depending on the specific use case, device, and JavaScript engine. These findings should not be taken as a definitive answer but rather as an indication of the relative performance differences between these two approaches.

Latest run results:

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

User agent: Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/117.0.0.0 Mobile Safari/537.36

Browser/OS: Chrome Mobile 117 on Android

View result in a separate tab

Test name	Executions per second
slice	1268753.0 Ops/sec
push	368252.8 Ops/sec

Related benchmarks:

Array slice vs for loop (set by index) (version: 0)

Comparing performance of: slice vs push

Created: one year ago by: Guest

Jump to the latest result

slice

push

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Sumamry (model llama3.1:latest, generated 4 days ago):