Benchmark: TEst pop vs .length -1

Script Preparation code:

var arr = [];
for (let i = 0; i < 1000000; i++) {
  arr.push(i);
}

Tests:

.length - 1
for (let i = 0; i < 1000000; i++) { const a = arr[arr.length - 1]; }
pop
for (let i = 0; i < 1000000; i++) { const a = arr.pop(); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
.length - 1
pop

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

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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's being tested.

**Benchmark Overview**

The benchmark measures the performance of two approaches to access the last element in an array:

1. Using `arr.length - 1` (indexing)
2. Using `arr.pop()` (array method)

**Library Used**

The benchmark uses the built-in JavaScript `Array` class, specifically the `push`, `pop`, and indexing operations.

**Indexing Approach (.length - 1)**

In this approach, a constant is assigned to the last element of the array by using the index `arr.length - 1`. This involves:

* Accessing the length property of the array (`arr.length`)
* Subtracting 1 from the length to get the index of the last element
* Assigning a value to the array at that index

Pros:

* Simple and straightforward approach
* Fast, as it only requires accessing an existing array element

Cons:

* May be slower for arrays with many elements due to the indexing operation
* Can lead to cache misses if the index is far away from the beginning of the array

**Array Method Approach (pop)**

In this approach, `arr.pop()` is called to remove and return the last element of the array. This involves:

* Calling the `pop` method on the array, which returns the last element
* Assigning the returned value to a constant

Pros:

* Fast, as it only requires calling an optimized method
* Does not involve indexing or accessing array elements directly

Cons:

* May be slower for arrays with many elements due to the method call and potential caching issues
* Requires a method call, which may incur additional overhead

**Other Considerations**

The benchmark also considers the device platform (Desktop) and operating system (Mac OS X 10.15.7), which may affect performance due to differences in hardware or software configurations.

**Alternatives**

Other approaches that could be used to access the last element of an array include:

* Using `arr[0]` followed by a method call (e.g., `array.shift()`), which would be slower than `pop`
* Using `splice(-1)` to remove and return the last element, which would be faster than `pop`, but may modify the original array
* Using a library like Lodash or Ramda, which provides optimized methods for accessing array elements

It's worth noting that in modern JavaScript, both approaches are generally accepted as equivalent and should perform similarly. However, the actual performance difference may vary depending on the specific use case and implementation details.

Related benchmarks:

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

Comparing performance of: .length - 1 vs pop

Created: 2 years ago by: Guest

Jump to the latest result

.length - 1

pop

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):