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

Tests:

Set length to zero
var size = 10000; var arr2 = []; for (var i = 0; i < size; i++){ arr2.push(i); } arr2.length = 0;
Splice
var size = 10000; var arr3 = []; for (var i = 0; i < size; i++){ arr3.push(i); } arr3.splice(0, arr3.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

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):

LLMs can make mistakes. Check important info.

Let's break down the JavaScript microbenchmark on MeasureThat.net.

**Benchmark Definition**

The benchmark is designed to compare two approaches for emptying an array in JavaScript: setting the `length` property of the array to 0, and using the `splice()` method with its first argument set to 0 and the second argument equal to the length of the array.

**Options Compared**

1. **Set length to zero**: This approach sets the `length` property of the array to 0, effectively emptying it.
2. **Splice**: This approach uses the `splice()` method with its first argument set to 0 (the index of the first element) and the second argument set to the length of the array, which removes all elements from the start of the array.

**Pros and Cons**

* **Set length to zero**:
	+ Pros: Simple, efficient, and widely supported.
	+ Cons: May not work as expected in some older browsers or with certain array implementations (e.g., `Array.prototype.slice()`).
* **Splice**:
	+ Pros: Works consistently across all browsers and array implementations.
	+ Cons: More complex and computationally expensive than setting the length property.

**Library Usage**

There is no explicit library usage in this benchmark. However, it's worth noting that some JavaScript engines (e.g., SpiderMonkey) have internal optimizations for certain operations, which may affect the benchmark results.

**Special JS Features or Syntax**

None are explicitly mentioned in the benchmark definition or individual test cases.

**Other Alternatives**

In addition to setting the `length` property and using `splice()`, other approaches to emptying an array include:

* Using `Array.prototype.length = 0;`
* Using `arr = new Array(size).fill(0);` (a more efficient approach that creates a new array with the desired length)
* Using `arr = arr.map((_, i) => { arr[i] = undefined; return i; });` (a more explicit approach using a map function)

Keep in mind that these alternatives may have varying levels of performance, compatibility, and code readability.

I hope this explanation helps!

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:109.0) Gecko/20100101 Firefox/115.0

Browser/OS: Firefox 115 on Mac OS X 10.15

View result in a separate tab

Test name	Executions per second
Set length to zero	18615.0 Ops/sec
Splice	20219.7 Ops/sec

Related benchmarks:

empty an array in JavaScript - splice vs setting length yonatan (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: one year ago by: Registered User

Jump to the latest result

Set length to zero

Splice

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):