Benchmark: Splice vs Pop for replacing last item

Script Preparation code:

var list = [];
for (var i = 0; i < 1000 * 1000; i++) {
  list.push(i);
}

Tests:

Pop + Concat
list.pop() list = list.concat(1)
Splice
list.splice(-1, 1, 1);
Pop + Push
list.pop() list.push(1)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Pop + Concat
Splice
Pop + Push

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/88.0.4324.182 Safari/537.36

Browser/OS: Chrome 88 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Pop + Concat	133.0 Ops/sec
Splice	1448588.8 Ops/sec
Pop + Push	7578379.5 Ops/sec

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

LLMs can make mistakes. Check important info.

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

**Benchmark Definition**

The benchmark definition represents three test cases:

1. **"Splice vs Pop for replacing last item"**: This is a broad description of the benchmark, indicating that it compares the performance of `splice` versus `pop` methods when used together to replace the last element in an array.
2. **Individual Test Cases**:
	* `"Pop + Concat"`: This test case measures the performance of `list.pop()` followed by `list.concat(1)`.
	* `"Splice"`: This test case measures the performance of `list.splice(-1, 1)` alone.
	* `"Pop + Push"`: This test case measures the performance of `list.pop()` followed by `list.push(1)`.

**Options Compared**

The benchmark compares three different approaches to replace the last element in an array:

1. **Using `splice`**: The `splice` method is used to remove and replace the last element at a specified index.
2. **Using `pop` followed by `concat`**: The `pop` method removes and returns the last element, which is then replaced with a new value using the `concat` method.
3. **Using `push`**: The `push` method adds a new element to the end of the array.

**Pros and Cons**

* **Using `splice`**: Pros:
	+ More efficient than `pop` followed by `concat`, as it only requires one operation.
	+ Can be faster for larger arrays, since it avoids creating a new array.
* **Using `pop` followed by `concat`**: Pros:
	+ Easier to understand and implement than using `splice`.
	+ Can be more intuitive for developers who are familiar with the `concat` method.
* **Using `push`**: Cons:
	+ Less efficient than `splice`, since it requires creating a new array element.
	+ May lead to slower performance for larger arrays.

**Library**

The benchmark uses the built-in JavaScript Array prototype, which provides methods for manipulating and accessing array elements. In this case, the `concat`, `splice`, and `push` methods are used to compare their performance in replacing the last element in an array.

**Special JS Feature/Syntax**

There is no specific JavaScript feature or syntax being tested in this benchmark. The focus is on comparing different approaches to replace the last element in an array using built-in Array prototype methods.

**Alternatives**

Other alternatives for replacing the last element in an array include:

* Using `slice()` and assigning a new value to the resulting array
* Using `set()` (available in modern browsers) and passing the new value as the second argument
* Using a custom implementation, such as using `indexOf` and `slice()`

However, these alternatives are not being tested in this benchmark.

Related benchmarks:

Splice vs Pop for replacing last item (version: 0)

Comparing performance of: Pop + Concat vs Splice vs Pop + Push

Created: 3 years ago by: Guest

Jump to the latest result

Pop + Concat

Splice

Pop + Push

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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