Benchmark: arr unshift vs push + reverse (small array)

Script Preparation code:

var arr = [10];

Tests:

unshift
for (let i = 0; i < 10; i++){ arr.unshift(i); }
push + reverse
for (let i = 0; i < 10; i++){ arr.push(i); } arr.reverse();

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
unshift
push + reverse

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 8 months ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/138.0.0.0 Safari/537.36

Browser/OS: Chrome 138 on Windows

View result in a separate tab

Test name	Executions per second
unshift	812.6 Ops/sec
push + reverse	1415.7 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what's being tested, compared, and their pros and cons.

**Benchmark Overview**

The benchmark is comparing two approaches to add an element to an array:

1. `unshift`: Adding an element to the beginning of the array using the `unshift` method.
2. `push + reverse`: Adding an element to the end of the array using the `push` method, followed by reversing the entire array.

**Library Used**

The benchmark doesn't explicitly mention any libraries being used beyond JavaScript's built-in functionality. However, it's likely that the browser's implementation of JavaScript is using a specific library or engine that might affect the results.

**Special JS Features or Syntax**

There are no special JavaScript features or syntaxes mentioned in this benchmark. The focus is on comparing two common array manipulation techniques.

**Options Compared**

The benchmark is comparing the performance of:

1. `unshift`: Adding an element to the beginning of the array.
2. `push + reverse`: Adding an element to the end of the array and then reversing the entire array.

**Pros and Cons of Each Approach**

* `unshift`:
	+ Pros: Can be faster for small arrays, as it only needs to shift elements to make room for the new element.
	+ Cons: Can be slower for large arrays, as it requires shifting all elements down, which can lead to more memory accesses and updates.
* `push + reverse`:
	+ Pros: Suitable for larger arrays, as it avoids the need to shift elements down.
	+ Cons: Slower than `unshift` because of the additional step of reversing the entire array.

**Other Considerations**

* The benchmark is using a small array (only 10 elements) which might not accurately represent real-world scenarios. Larger arrays would likely favor `push + reverse`.
* The use of `let i = 0;` for looping instead of traditional `for` loops might add additional overhead due to the need to create and initialize local scope variables.
* The benchmark doesn't account for any potential optimizations or caching that the browser's JavaScript engine might perform.

**Alternatives**

If you wanted to explore other array manipulation techniques, here are a few alternatives:

1. `splice`: Removing and replacing elements at specific indices.
2. `concat`: Adding one or more arrays together using concatenation.
3. `slice` with `push` (or vice versa): Using `slice` to create a new array from a subset of the original array, then pushing the elements onto the end.

These alternatives might offer different performance characteristics depending on the specific use case and array size.

Related benchmarks:

arr unshift vs push + reverse (small array) (version: 0)

Comparing performance of: unshift vs push + reverse

Created: 5 years ago by: Guest

Jump to the latest result

unshift

push + reverse

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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