Benchmark: Slice vs Index - MeasureThat.net

Tests:

Array Slice
const array = ['test','123','123','last']; const lastItem = array.slice(-1)[0];
Array Index
const array = ['test','123','123','last']; const lastItem = array[array.length - 1];

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array Slice
Array Index

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 16 days ago)

User agent: Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/135.0.0.0 Mobile Safari/537.36

Browser/OS: Chrome Mobile 135 on Android

View result in a separate tab

Test name	Executions per second
Array Slice	25482630.0 Ops/sec
Array Index	85392824.0 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks!

The provided JSON represents a benchmark test case on MeasureThat.net, where users can compare the performance of two approaches: using `array.slice()` and accessing the last element of an array by its index (`array[array.length - 1]`).

**What is being tested?**

In this benchmark, we're testing the performance difference between two ways to access the last element of an array:

1. Using `array.slice(-1)[0]`: This approach creates a new slice of the original array from the end (i.e., the last elements) and then extracts the first element (`[0]`) from that slice.
2. Accessing the last element by its index: `array[array.length - 1]`

**Options compared**

The benchmark is comparing two options:

* **Option A**: Using `array.slice(-1)[0]`
* **Option B**: Accessing the last element by its index (`array[array.length - 1]`)

**Pros and Cons of each approach:**

1. **Option A (Slice)**:
	* Pros:
		+ Creates a new slice, which can be useful for other operations on the original array.
		+ Can be more readable and explicit about intent.
	* Cons:
		+ Creates a new object in memory, which can lead to increased memory usage and garbage collection overhead.
		+ May incur additional overhead due to creating a new slice and then extracting the first element.
2. **Option B (Index)**:
	* Pros:
		+ Directly accesses the last element without creating any additional objects or slices.
		+ Can be more efficient in terms of memory usage and garbage collection.
	* Cons:
		+ Less readable and explicit about intent, as it requires understanding of array indexing.

**Other considerations:**

* The benchmark uses a small array (`['test','123','123','last']`) to minimize the impact of other factors on performance. This makes it easier to compare the relative performance of the two approaches.
* The benchmark doesn't use any external libraries or special JavaScript features that might affect performance.

**Library used:**

There are no explicit libraries mentioned in the benchmark, but MeasureThat.net itself uses a library or framework to execute and measure the benchmarks. However, this is not directly related to the specific benchmark being compared.

No special JavaScript features or syntax are explicitly used in the benchmark.

**Alternatives:**

If you're interested in exploring alternative approaches, here are a few:

* Using `Array.prototype.at()` (available in modern browsers and Node.js): This method returns the element at the specified index without creating a new slice.
* Using `Array.prototype.slice.call()` or `Array.prototype.slice.apply()`: These methods create a new array from an existing one, but they might have different performance characteristics depending on the browser or environment.

Keep in mind that these alternatives are not directly related to the specific benchmark being compared and would require additional modifications to measure their performance.

Related benchmarks:

Slice vs Index (version: 0)

Comparing performance of: Array Slice vs Array Index

Created: 2 years ago by: Guest

Jump to the latest result

Array Slice

Array Index

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):