Benchmark: clearing array via .length = 0 vs. = [] vs. .splice(0)

Script Preparation code:

var array = [];
for(let i = 0; i < 10000; i++){
  array.push(Math.random());
}

Tests:

length
let a = [...array]; a.length = 0;
reassignment
let a = [...array]; a = [];
.splice(0)
let a = [...array]; a.splice(0);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
length
reassignment
.splice(0)

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (X11; Linux x86_64; rv:100.0) Gecko/20100101 Firefox/100.0

Browser/OS: Firefox 100 on Linux

View result in a separate tab

Test name	Executions per second
length	9908.6 Ops/sec
reassignment	11057.4 Ops/sec
.splice(0)	11559.1 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what is being tested, compared, and other considerations.

**Benchmark Overview**

The provided JSON represents a JavaScript microbenchmark that compares three approaches to clear an array:

1. Using `array.length = 0`
2. Using `array = []` (reassignment)
3. Using `array.splice(0)` (removing elements from the start)

**Test Cases and Comparisons**

There are three test cases, each comparing a different approach to clearing the array.

* **"length"`: This test case compares the performance of using `array.length = 0` versus reassigning the array using `array = []`. The purpose is to measure which method is faster for a large array.
	+ Pros: Simple and easy to understand, no side effects on the original array.
	+ Cons: May not be as efficient due to the need to set the length property.
* **"reassignment"`: This test case compares the performance of reassigning the array using `array = []` versus using `array.splice(0)`. The purpose is to measure which method is faster for a large array.
	+ Pros: Efficient, as it directly changes the reference to an empty array, and doesn't require modifying the length property.
	+ Cons: Can be less intuitive for some developers, may not work in all situations (e.g., when working with immutable arrays).
* **".splice(0)"**: This test case compares the performance of using `array.splice(0)` versus reassigning the array using `array = []`. The purpose is to measure which method is faster for a large array.
	+ Pros: Efficient, as it directly removes elements from the start of the array, and doesn't require modifying the length property.
	+ Cons: May have performance overhead due to the creation of intermediate arrays or temporary variables.

**Library and Special JS Features**

There are no libraries used in this benchmark. However, it does utilize JavaScript features like:

* Array destructuring ( `let a = [...array];` )
* Length property (` array.length = 0;`)
* Reassignment syntax (` array = [];`)

These features are widely supported by modern browsers and are essential for many JavaScript applications.

**Other Alternatives**

If you're looking for alternatives to the provided benchmark, here are some options:

* Use a library like `benchmark.js`, which provides a more comprehensive set of testing tools and can handle a wide range of benchmarks.
* Create a custom benchmark using a framework like `jest` or `mocha`, which offer advanced features for writing and running tests.
* Consider using a different approach, such as measuring the performance of array operations using WebAssembly (WASM) or Native Modules.

Keep in mind that the choice of alternative will depend on your specific needs, experience, and goals.

Related benchmarks:

clearing array via .length = 0 vs. = [] vs. .splice(0) (version: 1)

Comparing performance of: length vs reassignment vs .splice(0)

Created: 2 years ago by: Registered User

Jump to the latest result

length

reassignment

.splice(0)

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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