Benchmark: .length vs overwrite array

Tests:

.length
let a = [1,2,3,4,5,6] a.length = 0;
overwrite
let a = [1,2,3,4,5,6] a = [];

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
.length
overwrite

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:106.0) Gecko/20100101 Firefox/106.0

Browser/OS: Firefox 106 on Linux

View result in a separate tab

Test name	Executions per second
.length	43534028.0 Ops/sec
overwrite	1698496256.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into explaining the provided benchmark.

The provided JSON represents a JavaScript microbenchmark, specifically measuring the performance difference between two approaches: using the `length` property of an array to reset its length and overwriting the entire array with an empty one.

**What is tested?**

The benchmark tests the following:

1. Using the `length` property (`let a = [1,2,3,4,5,6]\r\na.length = 0;`)
2. Overwriting the array with an empty one (`let a = [1,2,3,4,5,6]\r\na = [];`)

**Options compared**

Two approaches are compared:

1. Using `length` property to reset the array length
2. Overwriting the entire array with an empty one

**Pros and cons of each approach:**

1. **Using `length` property:**
	* Pros:
		+ More explicit and clear intent (i.e., setting the length to 0)
		+ May be faster since it only modifies the existing data
	* Cons:
		+ May not be as efficient for large arrays, as it only updates the internal array reference
2. **Overwriting with an empty array:**
	* Pros:
		+ More efficient for large arrays, as it creates a new array and copies the contents
	* Cons:
		+ Less explicit and may be slower due to the creation of a new array

**Library usage**

There is no explicit library mentioned in the benchmark definition. However, the benchmarks are likely using the V8 JavaScript engine, which is a popular and widely-used engine.

**Special JS feature or syntax**

None mentioned.

**Other alternatives**

The benchmark could have used other approaches, such as:

1. Using `splice()` to remove all elements from the array
2. Using `map()` and `filter()` with an empty callback function
3. Using `slice()` and assignment

However, these alternatives are not explicitly tested in this benchmark.

In summary, the benchmark measures the performance difference between two approaches: using the `length` property to reset an array's length and overwriting the entire array with an empty one. The pros and cons of each approach are discussed, and the library used is likely V8.

Related benchmarks:

.length vs overwrite array (version: 0)

Comparing performance of: .length vs overwrite

Created: 2 years ago by: Registered User

Jump to the latest result

.length

overwrite

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):