Benchmark: splice vs unshift by winensf

Script Preparation code:

const x = [];
for (var i = 0; i < 20000; i++) {
    x.push(i);
}

Tests:

splice
const x = []; for (var i = 0; i < 20000; i++) { x.push(i); } for(var i = 0; i < 50; i++){ x.splice(20000+i-1, 0, 20000+i) }
unshift
const x = []; for (var i = 0; i < 20000; i++) { x.push(i); } for(var i = 0; i < 50; i++){ x.unshift(20000+i) }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
splice
unshift

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 16_1_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/16.1 Mobile/15E148 Safari/604.1

Browser/OS: Mobile Safari 16 on iOS 16.1.1

View result in a separate tab

Test name	Executions per second
splice	12465.3 Ops/sec
unshift	4764.4 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the explanation of the provided benchmark.

**Benchmark Overview**

The benchmark is comparing two approaches to add elements to an array: `splice` and `unshift`. The test creates an array of 20,000 elements using a loop and then performs either one of these operations 50 times on the array.

**Options Compared**

Two options are being compared:

1. **Splice**: This method modifies the original array by inserting or removing elements at a specified position. In this benchmark, it's used to insert 50 new elements at the end of the array.
2. **Unshift**: This method adds one or more elements to the beginning of an array and returns the modified array.

**Pros and Cons**

* **Splice**:
	+ Pros: Can be efficient for large arrays as it only requires updating references to existing elements.
	+ Cons: Can lead to slower performance if the array is very large due to the need to update all elements' indices. Additionally, `splice` can be more error-prone than `unshift` since it modifies the original array and doesn't provide a clear indication of what's being added or removed.
* **Unshift**:
	+ Pros: Provides a predictable and efficient way to add elements to an array at the beginning. It also allows for better code readability and maintainability since the new elements are added without modifying existing indices.
	+ Cons: Requires creating a new array with the additional elements, which can be more memory-intensive than `splice`.

**Library**

There is no explicit library mentioned in the benchmark definition or test cases. However, it's likely that the implementation uses built-in JavaScript methods for arrays.

**Special JS Feature/Syntax**

None are explicitly mentioned, but keep in mind that some browsers may have performance differences due to specific features like Safari's WebKit engine or Chrome's V8 engine.

**Other Considerations**

The benchmark is designed to measure the performance of these two array operations on a modern JavaScript environment. The results will provide insight into which approach is more efficient for adding elements to an array in different scenarios.

As for alternatives, other methods for adding elements to an array include:

* `concat()`: Creates a new array by concatenating the original array with the new elements.
* `Array.prototype.push()` and subsequent calls: While similar to `splice`, this approach modifies the original array but requires more function calls, which can lead to slower performance.

To further explore these benchmarks, you can use tools like BenchmarkJS or microbenchmark.net to run multiple test cases on different environments and browsers.

Related benchmarks:

splice vs unshift by winensf (version: 0)

bla bla

Comparing performance of: splice vs unshift

Created: 2 years ago by: Guest

Jump to the latest result

splice

unshift

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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