Benchmark: array.length vs array.splice

Script Preparation code:

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

Tests:

Deleting through length
sut.length = 10;
Deleting through spclie
sut.splice(10, 9000);
Slicing
sut.slice(10);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Deleting through length
Deleting through spclie
Slicing

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):

LLMs can make mistakes. Check important info.

**Benchmark Overview**

The provided JSON represents a JavaScript microbenchmarking test case for measuring the performance of three different approaches to delete elements from an array: `length`, `splice`, and `slice`.

**Tested Options**

The benchmark compares the execution time of deleting the last 9000 elements from an array using:

1. **`length`**: Using the length property to set the length of the array, which effectively removes all elements after a certain index.
2. **`splice`**: Using the `splice()` method with negative indices to delete elements from the end of the array.
3. **`slice`**: Using the `slice()` method with a start index equal to the desired offset to create a new array, effectively removing all elements before that index.

**Pros and Cons**

* **`length`**: This approach is simple and efficient but can be slow for large arrays since it involves setting the length property of the array, which may trigger garbage collection.
* **`splice`**: This approach is more flexible and allows for partial deletion, but its performance may degrade as the number of elements to delete increases. It also modifies the original array.
* **`slice`**: This approach creates a new array without modifying the original, making it suitable for large arrays. However, it requires creating a new object in memory.

**Library and Special JS Features**

None mentioned in the provided JSON.

**Other Considerations**

When comparing performance, other factors such as:

* Array size: Larger arrays may require more time to process.
* Browser engine: Different browsers may execute JavaScript differently.
* Garbage collection: Frequent deletion of elements can trigger garbage collection, which may impact performance.

**Alternatives**

If you need to delete large numbers of elements from an array efficiently, consider using:

1. **`filter()`**: Instead of deleting elements, use the `filter()` method to create a new array with only the desired elements.
2. **`map()`**: Use the `map()` method to create a new array with transformed data, effectively removing unwanted elements.
3. **NativeArray methods**: Some browsers have native methods like `splice()` and `slice()` optimized for performance.

In conclusion, the benchmark provides valuable insights into the performance differences between these three approaches to delete elements from an array. By considering factors such as array size, browser engine, and garbage collection, you can make informed decisions about which approach is best suited for your specific use case.

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/128.0.0.0 Safari/537.36 Edg/128.0.0.0

Browser/OS: Chrome 128 on Windows

View result in a separate tab

Test name	Executions per second
Deleting through length	17404136.0 Ops/sec
Deleting through spclie	19989112.0 Ops/sec
Slicing	20877090.0 Ops/sec

Related benchmarks:

array.length vs array.splice (version: 0)

Want to make sure that delete last elements through length is faster.

Comparing performance of: Deleting through length vs Deleting through spclie vs Slicing

Created: 3 years ago by: Registered User

Jump to the latest result

Deleting through length

Deleting through spclie

Slicing

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):