Benchmark: pop() vs array.length - 1

Tests:

Array.pop()
let array = new Array(25) const arrayLastItem = array.pop()
Array[Array.length - 1]
let array = new Array(25) const arrayLastItem = array[array.length - 1]

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array.pop()
Array[Array.length - 1]

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 3 months ago)

User agent: Mozilla/5.0 (Linux; Android 11; M2103K19G) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/114.0.0.0 Mobile Safari/537.36

Browser/OS: Chrome Mobile 114 on Android

View result in a separate tab

Test name	Executions per second
Array.pop()	18523698.0 Ops/sec
Array[Array.length - 1]	21079108.0 Ops/sec

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

LLMs can make mistakes. Check important info.

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

**What is tested?**

The benchmark measures the performance difference between two approaches when accessing the last element of an array:

1. Using `array.pop()`: This method removes and returns the last element from the array.
2. Using `array[array.length - 1]`: This syntax directly accesses the last element of the array without removing it.

**Options compared**

The benchmark compares these two approaches because `pop()` has a time complexity of O(1), whereas accessing an element by its index (`array[array.length - 1]`) also has a constant time complexity, but requires additional overhead due to indexing and potential bounds checking. The goal is to determine which approach is faster.

**Pros and Cons of each approach:**

* `array.pop()`:
	+ Pros:
		- Only removes the last element from the array.
		- Can be more convenient for certain use cases (e.g., when you want to remove the last item).
	+ Cons:
		- May require re-allocating memory, which can lead to performance issues with large arrays.
		- Can affect array length and indices of subsequent elements.
* `array[array.length - 1]`:
	+ Pros:
		- Leaves the original array intact.
		- Provides a direct and simple way to access the last element without removing it.
	+ Cons:
		- May incur additional overhead due to indexing and bounds checking.

**Library usage**

In the benchmark definition, there is no library mentioned. Both approaches only use built-in JavaScript features.

**Special JS feature or syntax**

There are no special features or syntaxes used in this benchmark. It's a simple comparison of two basic array access methods.

**Other alternatives**

If you were to modify this benchmark to explore other aspects, you might consider comparing:

* `array[0]` vs `array[array.length - 1]`: This would compare the performance of accessing the first element versus the last element.
* `slice()` vs `.pop()`: If you wanted to measure the performance of array methods that remove elements versus direct indexing or pop().

Keep in mind that these alternatives may not be directly related to the original question, but they could provide additional insights into the performance characteristics of different JavaScript array access methods.

Related benchmarks:

pop() vs array.length - 1 (version: 0)

Comparing performance of: Array.pop() vs Array[Array.length - 1]

Created: 2 years ago by: Guest

Jump to the latest result

Array.pop()

Array[Array.length - 1]

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):