Benchmark: empty an array in JavaScript?

Script Preparation code:

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

Tests:

Just instantiate new array
arr = [];
Set length to zero
arr.length = 0;
Splice
arr.splice(0, arr.length);
Slice
arr = arr.slice(10);
splice 0
arr.splice(0);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Just instantiate new array
Set length to zero
Splice
Slice
splice 0

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

**Overview of the Benchmark**

The provided JSON represents a JavaScript benchmark that tests how different methods are used to empty an array in JavaScript. The benchmark was designed to answer a question on Stack Overflow, as indicated by the "Description" field.

**Options Compared in the Benchmark**

The benchmark compares four options for emptying an array:

1. **Just instantiate a new array**: `arr = []`
2. **Set length to zero**: `arr.length = 0`
3. **Splice method with a single argument (0)**: `arr.splice(0)`
4. **Slice method with a negative start index (10)**: `arr.slice(10)`

**Pros and Cons of Each Approach**

1. **Just instantiate a new array**: This approach is simple and efficient, as it doesn't modify the existing array.
	* Pros: Fastest execution time
	* Cons: Creates a new array object, which can be memory-intensive for large arrays
2. **Set length to zero**: This approach modifies the existing array by setting its length to zero.
	* Pros: Only creates a temporary variable, so it's relatively lightweight
	* Cons: Can cause issues if the array has been previously modified or if it's used in certain contexts (e.g., as an object key)
3. **Splice method with a single argument (0)**: This approach modifies the existing array by removing its first element.
	* Pros: Removes elements from the end of the array, which can be beneficial for large arrays
	* Cons: Can cause issues if the array is modified elsewhere in the code
4. **Slice method with a negative start index (10)**: This approach creates a new array that contains a subset of elements from the original array.
	* Pros: Creates a new array object, which can be beneficial for large arrays
	* Cons: Can be slower than other methods if the slice size is small

**Library Used**

The benchmark does not use any libraries explicitly. However, it's worth noting that some browsers (like Chrome) have built-in optimizations for certain JavaScript features, such as array methods.

**Special JS Feature or Syntax**

None of the provided benchmark test cases use special JavaScript features or syntax beyond standard ECMAScript.

Latest run results:

Run details: (Test run date: 2025 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36

Browser/OS: Chrome 63 on Mac OS X 10.13.1

View result in a separate tab

Test name	Executions per second
Just instantiate new array	7784635.0 Ops/sec
Set length to zero	6402263.5 Ops/sec
Splice	3030828.5 Ops/sec
Slice	3540259.8 Ops/sec
splice 0	4118279.8 Ops/sec

Related benchmarks:

empty an array in JavaScript? (version: 1)

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

Comparing performance of: Just instantiate new array vs Set length to zero vs Splice vs Slice vs splice 0

Created: 6 years ago by: Registered User

Jump to the latest result

Just instantiate new array

Set length to zero

Splice

Slice

splice 0

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):