Benchmark: JS Array Clearing

Script Preparation code:

var a = [];
for (var i=0; i < 1000000;i++){
  a.push("item"+i);
}

Tests:

Length = 0
a.length = 0;
Splice
a.splice(0, a.length-1);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Length = 0
Splice

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/134.0.0.0 Safari/537.36

Browser/OS: Chrome 134 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Length = 0	39319436.0 Ops/sec
Splice	53635176.0 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.

**Benchmark Overview**

The test case, titled "JS Array Clearing," measures the performance of clearing an array in JavaScript. The script preparation code creates an empty array `a` and then populates it with 1 million elements using a loop. This setup simulates a common scenario where large arrays need to be processed.

**Comparison Options**

The benchmark compares two approaches:

1. **Length = 0**: This option tests setting the length of the array to 0. It's likely being tested because it's an efficient way to clear an array, as it doesn't require modifying individual elements.
2. **Splice(0, a.length-1)**: This option uses the `splice` method with arguments `(0, a.length-1)`, which removes all elements from the array starting at index 0.

**Pros and Cons**

* **Length = 0**: Pros:
	+ Fastest execution time (as seen in the benchmark result).
	+ Low overhead, as it only updates the `length` property.
* **Splice(0, a.length-1)**: Pros:
	+ Can be used to remove elements from an array while preserving other elements.
	+ May be slightly faster than `length = 0` for very large arrays due to cache locality.

Cons:

* **Length = 0**: May cause issues in older browsers or environments that don't support the `length` property being set.
* **Splice(0, a.length-1)**: Can lead to performance issues if used excessively, as it involves modifying the array's internal structure. Additionally, modern browsers have optimized `splice` for large arrays.

**Other Considerations**

The benchmark doesn't consider other methods for clearing an array, such as using `array.prototype.fill()` or `array.prototype.map()`. These alternatives may be worth exploring in a real-world scenario.

**Library and Special JS Features**

There are no libraries mentioned in the benchmark definition. However, if you were to use a library like Lodash, you might consider `lodash.eachRight()` for array clearing.

The benchmark doesn't require any special JavaScript features or syntax beyond what's available in modern browsers.

**Alternatives**

Other alternatives for clearing an array include:

* Using `array.prototype.fill(0)` (filling the array with zeros) followed by `array.prototype.splice()`
* Using `array.prototype.map()` to create a new array containing only zeros
* Using `array.prototype.reduce()` to clear the array

Keep in mind that these alternatives may have performance implications and might not be suitable for all use cases.

In summary, the benchmark tests two common approaches for clearing an array: setting the length to 0 and using `splice(0, a.length-1)`. The choice of approach depends on specific requirements and browser support considerations.

Related benchmarks:

JS Array Clearing (version: 0)

Comparing performance of: Length = 0 vs Splice

Created: 4 years ago by: Guest

Jump to the latest result

Length = 0

Splice

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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