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

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);

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 one month ago):

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what's being tested, compared options, pros and cons of each approach, and other considerations.

**Benchmark Definition**

The benchmark is designed to measure the performance difference between two methods for emptying an array in JavaScript:

1. Setting the `length` property to 0.
2. Using the `splice()` method with no arguments (i.e., `splice(0)`).

**Test Cases**

There are two test cases:

1. "Set length to zero":
	* The script prepares a large array (`arr2`) by pushing 10,000 elements onto it using a loop.
	* Then, it sets the `length` property of `arr2` to 0.
	* The goal is to measure how quickly this operation can be performed.
2. "Splice":
	* Similar to the first test case, but instead of setting the `length` property, it uses `splice(0)` to clear the array.

**Options Compared**

The two options being compared are:

1. Setting the `length` property to 0.
	* This method is relatively simple and efficient, as it only requires updating a single value in the array's metadata.
2. Using the `splice()` method with no arguments (i.e., `splice(0)`).
	* This method creates a new empty array by copying the elements from the original array to a new location.

**Pros and Cons**

**Setting the `length` property:**

Pros:

* Fast, as it only involves updating an internal value.
* Efficient in terms of memory usage, as it doesn't create a new array.

Cons:

* May not work correctly if the array is sparse (i.e., has gaps in its indices).
* Can be less intuitive for developers who are not familiar with this method.

**Using `splice(0)`:**

Pros:

* More intuitive and easier to understand, as it clearly indicates that an empty array is being created.
* Works correctly even if the array is sparse.

Cons:

* Creates a new empty array, which can be more memory-intensive than setting the `length` property directly.
* Can be slower due to the overhead of creating a new array.

**Other Considerations**

Both methods have their trade-offs in terms of performance and memory usage. The choice between them may depend on specific use cases or requirements.

Additionally, it's worth noting that other methods for emptying an array, such as using `fill()` with a zero value, are not being tested in this benchmark. However, these alternatives might be worth exploring in their own right.

**Libraries and Special JS Features**

There are no libraries explicitly mentioned in the benchmark definition or test cases. However, some JavaScript engines (like V8) optimize certain operations for specific platforms or architectures. For example, setting the `length` property might have different performance characteristics on a 32-bit vs. 64-bit platform.

**Alternative Benchmarks**

Other benchmarks that could be relevant to this topic include:

* "Array initialization vs. array concatenation"
* "Array length optimization techniques"
* "JavaScript array operations: a comprehensive benchmark"

These alternative benchmarks would explore other aspects of JavaScript array performance and might provide more insight into the trade-offs involved in choosing different methods for emptying an array.

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/18.0.1 Safari/605.1.15

Browser/OS: Safari 18 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Set length to zero	41293.1 Ops/sec
Splice	27575.7 Ops/sec

Related benchmarks:

empty an array in JavaScript - splice vs setting length (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: 4 years ago by: Guest

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 one month ago):