Benchmark: array.splice vs for loop

Script Preparation code:

s = new Set();
a = [];
for (var i=0; i < 1000; i++) s.add(i*i);

Tests:

array.splice
a.splice(0, a.length, ...s.values());
for loop
a.length = 0; for (var x of s) a.push(x);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
array.splice
for loop

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/123.0.0.0 Mobile Safari/537.36

Browser/OS: Chrome Mobile 123 on Android

View result in a separate tab

Test name	Executions per second
array.splice	21987.6 Ops/sec
for loop	6757.1 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's being tested.

**Benchmark Overview**

The benchmark compares the performance of two approaches for populating an array `a` with values from a set `s`. The set is populated with squares of numbers from 0 to 999 using JavaScript syntax.

**Approaches Compared**

There are two test cases:

1. **Array Splice (`array.splice`)**: This approach uses the `splice()` method to replace the contents of array `a` with values from the set `s`. The `splice()` method takes three arguments: the starting index, the number of elements to remove, and a list of new elements.
2. **For Loop (`for loop`)**: This approach iterates over the set `s` using a `for...of` loop and pushes each value onto array `a`.

**Pros and Cons**

1. **Array Splice**
	* Pros:
		+ Can be more efficient if the length of `a` is known in advance.
		+ Uses less memory, as it doesn't create temporary arrays.
	* Cons:
		+ Requires modifying the original array.
		+ May have performance issues if the set `s` has a large number of elements.
2. **For Loop**
	* Pros:
		+ More predictable and controlled iteration.
		+ Uses more memory, as an intermediate array is created to hold the values from `s`.
	* Cons:
		+ May be slower due to the overhead of creating a temporary array.

**Other Considerations**

* The benchmark uses the `Set` data structure to populate the array with unique values. This helps to ensure that each value in `a` is distinct.
* The `for...of` loop is used to iterate over the set, which is more efficient than using traditional indexing.

**Special JavaScript Features/Syntax**

None mentioned.

**Library/Functionality Used**

The benchmark uses a built-in JavaScript feature: the `Set` data structure and the `splice()` method. There are no external libraries required.

**Alternative Approaches**

Other alternatives could include:

1. Using an array constructor, such as `new Array()`, to create a new array from scratch.
2. Using the `Array.from()` method to create an array from the set.
3. Iterating over the set using traditional indexing (e.g., `for (var i = 0; i < s.size(); i++)`).

These alternatives would likely have different performance characteristics and trade-offs compared to the approaches tested in this benchmark.

Related benchmarks:

array.splice vs for loop (version: 0)

Comparing performance of: array.splice vs for loop

Created: 9 years ago by: Guest

Jump to the latest result

array.splice

for loop

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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