Benchmark: Testing pop vs index-again

Script Preparation code:

var arr1 = [0,1,2,3,4,5,6,7,8,9];
var arr2 = [];

function popLast(arr, n) {
  const element = arr.pop();
  return element === n;
}

function indexLast(arr, n) {
  const element = arr[n-1];
  return element === n;
}

Tests:

Pop test
popLast(arr1, 9)
Index test
indexLast(arr1, 9)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Pop test
Index test

Fastest: N/A

Slowest: N/A

Latest run results:

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

LLMs can make mistakes. Check important info.

I'd be happy to explain the benchmark and its results.

**Benchmark Overview**

The provided benchmark measures the performance of two JavaScript functions, `popLast` and `indexLast`, on an array `arr1` containing 10 elements. The goal is to determine which approach is faster for checking if the last element in the array matches a given value `n`.

**Options Compared**

There are two options compared:

1. **Pop Last**: This function uses the `pop()` method to remove and return the last element from the array, then checks if it matches the value `n`.
2. **Index Last**: This function accesses the last element of the array using an index (`arr[n-1]`) and checks if it matches the value `n`.

**Pros and Cons**

* **Pop Last**:
	+ Pros: Simple and straightforward implementation.
	+ Cons: Creates a new array object when popping the last element, which can lead to unnecessary memory allocation and deallocation. Additionally, the `pop()` method may not be optimized for performance.
* **Index Last**:
	+ Pros: Does not create a new array object and is likely to be more efficient since it only accesses an existing element.
	+ Cons: Requires manual indexing, which can lead to errors if the index calculation is incorrect.

**Library and Special JS Features**

Neither of the functions uses any external libraries. However, they do utilize a special JavaScript feature:

* **Array Pop**: The `pop()` method on arrays is a built-in JavaScript method that removes and returns the last element from an array.
* **Array Indexing**: Array indexing (e.g., `arr[n-1]`) is a fundamental concept in JavaScript for accessing elements within an array.

**Benchmark Results**

The benchmark results show that:

* The **Index Last** approach outperforms the **Pop Last** approach, with approximately 5.7x faster execution times.
* Both tests are executed on Firefox 119 on a desktop platform running Linux.

**Other Alternatives**

If you were to consider alternative approaches, here are a few options:

1. Use `unshift()` and check if the first element matches: This method would also remove the last element from the array but in reverse order.
2. Use `splice()` to remove the last element: This method would be similar to `pop()`, but with more overhead due to its implementation.
3. Use a custom loop to iterate through the array: This approach would not rely on built-in methods like `pop()` or indexing, which could potentially lead to slower performance.

However, given the simplicity and optimization of the `indexLast` function, it is likely that this will remain the fastest approach for most use cases.

Related benchmarks:

Testing pop vs index-again (version: 0)

Comparing performance of: Pop test vs Index test

Created: 2 years ago by: Guest

Jump to the latest result

Pop test

Index test

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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