Benchmark: empty an array in JavaScript - splice vs setting length faster

Script Preparation code:

var size = 10000;
var arr = [];
for (var i = 0; i < size; i++){
  arr.push(i);
}

Tests:

Set length to zero
arr.length = 0;
Splice
arr.splice(0, arr.length);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Set length to zero
Splice

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/145.0.0.0 Safari/537.36

Browser/OS: Chrome 145 on Windows

View result in a separate tab

Test name	Executions per second
Set length to zero	23012442.0 Ops/sec
Splice	30456768.0 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 benchmark and explain what's being tested.

**Benchmark Definition**

The benchmark is testing two different approaches to empty an array in JavaScript:

1. `arr.length = 0;`
2. `arr.splice(0, arr.length);`

**Options Compared**

The two options are compared in terms of performance, specifically execution speed.

* Option 1: Setting the length of the array to 0 using `arr.length = 0;`. This is a simple and direct way to set the length of an array.
* Option 2: Using `splice(0, arr.length);` to remove all elements from the beginning of the array. This method also sets the length of the array but uses a more efficient algorithm.

**Pros and Cons**

Here's a brief summary of the pros and cons of each approach:

* **Option 1 (arr.length = 0;)**:
	+ Pros: Simple, straightforward, and easy to implement.
	+ Cons: May not be as efficient for large arrays, as it involves a separate operation to update the array length.
* **Option 2 (splice(0, arr.length);)**:
	+ Pros: More efficient than setting the length directly, especially for large arrays. It also uses less memory, as it only updates the length of the array without creating a new one.
	+ Cons: May be slightly more complex to implement, and some older browsers may not support `splice` or have performance issues with it.

**Library Usage**

There is no explicit library usage in this benchmark. However, if you're using a JavaScript environment that doesn't support `splice`, you might need to use a polyfill or alternative implementation.

**Special JS Feature/Syntax**

This benchmark doesn't use any special JavaScript features or syntax beyond what's required for the comparison (i.e., `splice`). If it did, I'd be happy to explain!

**Other Alternatives**

If you're interested in exploring other approaches, here are some alternatives:

* Using a custom loop to iterate over the array and remove elements: `for (var i = 0; i < arr.length; i++) { arr.splice(i, 1); }`
* Using `fill()` method with an empty value: `arr.fill(undefined)`
* Using `map()` function and then `set()`: `arr.map(() => undefined).forEach((_, index) => set(arr[index], null))`

Keep in mind that these alternatives might have different performance characteristics or require additional setup.

I hope this explanation helps you understand the benchmark better!

Related benchmarks:

empty an array in JavaScript - splice vs setting length faster (version: 0)

Based on question on http://stackoverflow.com/questions/1232040/how-do-i-empty-an-array-in-javascript

Comparing performance of: Set length to zero vs Splice

Created: 2 years ago by: Guest

Jump to the latest result

Set length to zero

Splice

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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