Benchmark: array.length = 0 vs []

Script Preparation code:

var arr = [1,2,3,4];

Tests:

array length = 0
arr.length = 0
array = []
arr = []

Historical Performance Data aggregated from 16 community runs

Desktop Results:

Chrome 10 runs

array length = 0

17.7M/s

array = []

7.9M/s

Fastest: array length = 0 (2.2x faster)

View exact numbers

✓ array length = 0: 17,673,226 ops/sec
• array = []: 7,879,055 ops/sec

Firefox 6 runs

array = []

111.3M/s

array length = 0

45.7M/s

Fastest: array = [] (2.4x faster)

View exact numbers

✓ array = []: 111,264,496 ops/sec
• array length = 0: 45,674,008 ops/sec

Results show median performance across all community submissions. Run this benchmark yourself to verify on your device.

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
array length = 0
array = []

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 6 months ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/144.0.0.0 Safari/537.36

Browser/OS: Chrome 144 on Windows

View result in a separate tab

array length = 0

18.5M/s

array = []

5.8M/s

View exact numbers

Test name	Executions per second
✓ array length = 0	18,496,626 Ops/sec
array = []	5,769,134 Ops/sec

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

LLMs can make mistakes. Check important info.

I'd be happy to explain what's being tested in the provided JSON benchmark.

**Overview**

The benchmark is designed to compare the performance of two approaches: accessing the length property of an empty array (`arr.length = 0`) and creating an empty array using the literal syntax (`arr = []`).

**What's being tested?**

When you run a JavaScript code, the engine needs to execute it. In this case, we're interested in measuring how fast each approach can be executed.

1. **`arr.length = 0`**: This approach tests whether accessing the length property of an empty array (`arr`) is faster than not doing anything (i.e., no operation).
2. **`arr = []`**: This approach tests whether creating a new, empty array using the literal syntax (`arr = []`) is faster than not doing anything.

**Options compared**

The benchmark compares two options:

* Accessing `arr.length = 0`: This option checks if accessing an empty array's length property is fast.
* Creating an empty array (`arr = []`): This option checks if creating a new, empty array using the literal syntax is faster than not doing anything.

**Pros and Cons**

Here are some pros and cons of each approach:

1. **Accessing `arr.length = 0`**:
	* Pros: Simple and easy to understand.
	* Cons: Might be slower due to accessing an attribute, which can incur a small overhead.
2. **Creating an empty array (`arr = []`)**:
	* Pros: Can be faster because it's a single operation that creates a new object.
	* Cons: Requires understanding the syntax and might not be as readable.

**Library and Special JS Features**

There is no library mentioned in this benchmark, but it does involve JavaScript features like array literals (`arr = []`) and property access (`arr.length`).

**Other Alternatives**

If you wanted to write a similar benchmark, you could also compare:

* Using `new Array(0)` instead of `[]`
* Using `Array(0)` (an older syntax) instead of `[]`
* Accessing an array's length using `arr[0]` or other methods

Keep in mind that these alternatives might have different performance characteristics and are not necessarily equivalent to the original approaches.

**Additional Considerations**

When writing a benchmark like this, consider factors like:

* Hardware: Different devices and browsers may exhibit varying performance.
* JavaScript engine: The specific JavaScript engine used can affect execution speed.
* Code quality: Write clean, readable code that minimizes overhead.

By understanding what's being tested in this benchmark, you'll be better equipped to write efficient and performant JavaScript code.

array.length = 0 vs [] (version: 0)

Comparing performance of: `array length = 0 vs array = []`

Created: one year ago by: Guest

Go to the latest result

array length = 0

array = []

Historical Performance Data aggregated from 16 community runs

Desktop Results:

Chrome 10 runs

Firefox 6 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

array.length = 0 vs [] (version: 0)

Comparing performance of: array length = 0 vs array = []

Created: one year ago by: Guest

Go to the latest result

array length = 0

array = []

Historical Performance Data aggregated from 16 community runs

Desktop Results:

Chrome 10 runs

Firefox 6 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

Related benchmarks

Comparing performance of: `array length = 0 vs array = []`