Benchmark: Slice vs Pop vs index

Script Preparation code:

var arr = ["https:/","/","measurethat.net/","Benchmarks/","Fork"];

Tests:

Slice
arr.slice(-1);
Pop
arr.pop();
index
arr[arr.length-1]

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Slice
Pop
index

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36

Browser/OS: Chrome 120 on Mac OS X 10.15.7

View result in a separate tab

Pop

27.2M/s

Slice

17.7M/s

index

9.1M/s

View exact numbers

Test name	Executions per second
✓ Pop	27,202,092 Ops/sec
Slice	17,710,992 Ops/sec
index	9,076,891 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 is being tested, along with the pros and cons of each approach.

**Benchmark Overview**

The benchmark tests three ways to access the last element of an array in JavaScript:

1. `arr.slice(-1)`
2. `arr.pop()`
3. `arr[arr.length-1]`

These methods are compared to determine which one is the fastest and most efficient.

**Options Compared**

* **`arr.slice(-1)`**: This method creates a new array with the last element of the original array.
* **`arr.pop()`**: This method removes and returns the last element of the array, without creating a new array.
* **`arr[arr.length-1]`**: This method accesses the last element of the array by using the array's length property.

**Pros and Cons**

* **`arr.slice(-1)`**:
	+ Pros: Creates a shallow copy of the entire array with only the last element, which can be useful in certain scenarios.
	+ Cons: Returns a new array object, which can be memory-intensive if dealing with large arrays. It's also slower than `arr.pop()` because it involves creating a new array.
* **`arr.pop()`**:
	+ Pros: Does not create a new array, making it more memory-efficient and faster than `arr.slice(-1)`.
	+ Cons: Removes the last element from the original array, which can be problematic if the array is used elsewhere. Also, some older browsers might not support this method.
* **`arr[arr.length-1]`**:
	+ Pros: Fast and efficient, as it only accesses the last element directly without creating a new array or modifying the original array.
	+ Cons: Can lead to incorrect behavior if the array is modified while accessing its elements. This method assumes that the array's length never changes.

**Library and Special JS Features**

There are no external libraries used in this benchmark. However, it's worth noting that some JavaScript engines might have special optimizations or features for certain methods (e.g., `arr.pop()`), but these are not specific to any library.

**Other Alternatives**

If you need more control over array manipulation or performance optimizations, consider using:

* **`Array.prototype.lastIndexOf()`**: This method returns the index of the last occurrence of a specified value in an array. It's generally slower than accessing the last element directly with `arr[arr.length-1]`.
* **`Array.prototype.splice()`**: This method removes and replaces elements from an array, returning an array of removed elements. While it can be useful in certain scenarios, it's not typically used for simple access to the last element.

In summary, when working with arrays in JavaScript, `arr[arr.length-1]` is usually the fastest way to access the last element without creating a new array or modifying the original one. However, if you need more control over memory usage or want to ensure that the last element is returned safely, `arr.slice(-1)` might be a better choice. Always consider the trade-offs between speed, memory efficiency, and code readability when selecting an approach for your specific use case.

Slice vs Pop vs index (version: 0) Benchmark.js

Comparing performance of: `Slice vs Pop vs index`

Created: 5 years ago by: Guest

Go to the latest result

Slice

Pop

index

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

Slice vs Pop vs index (version: 0) Benchmark.js

Comparing performance of: Slice vs Pop vs index

Created: 5 years ago by: Guest

Go to the latest result

Slice

Pop

index

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: `Slice vs Pop vs index`