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

Script Preparation code:

var arr = [10];

AخA
 
var arr = [10];

Tests:

unshift

for (let i = 0; i < 100000; i++){
  arr.unshift(i);
}

 
for (let i = 0; i < 100000; i++){  arr.unshift(i);}

push + reverse
for (let i = 0; i < 100000; i++){ arr.push(i); } arr.reverse();
for (let i = 0; i < 100000; i++){
arr.push(i);
}
arr.reverse();

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Experimental features:

Memory measurements supported only in Chrome.
For precise memory measurements Chrome must be launched with --enable-precise-memory-info flag.
More information: Monitoring JavaScript Memory

Test case name	Result
unshift
push + reverse

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 11 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/123.0.0.0 Safari/537.36

Browser/OS: Chrome 123 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
unshift	0.2 Ops/sec
push + reverse	60.4 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 4 months ago):

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

Benchmark Overview

The benchmark measures the performance of two JavaScript operations on large arrays: unshift and push + reverse. The test cases create a small initial array with 10 elements and then either use unshift to add 100,000 elements from scratch or use push followed by reverse to add the same amount of elements in reverse order.

Approaches Compared

unshift: This operation adds an element to the end of the array without shifting existing elements. It's a relatively simple and efficient operation.
push + reverse: This approach uses push to add elements to the end of the array, followed by reverse to rearrange the elements in reverse order.

Pros and Cons

unshift:
- Pros: Simple, fast, and efficient ( O(1) average case).
- Cons: May not be suitable for arrays with many existing elements, as it can lead to fragmentation.
push + reverse:
- Pros: Can handle large arrays with many existing elements, as push doesn't affect the indexing of existing elements. Also, reverse can take advantage of JavaScript's caching mechanisms for reversals.
- Cons: More complex and slower than unshift, especially for small to medium-sized arrays.

Other Considerations

Array size: The benchmark creates a large array with 100,000 elements. This is likely done to minimize the impact of array resizing or reallocation, which can be expensive operations.
JavaScript engine: The benchmark is run on Chrome 123, which may not be the most recent version. Additionally, the RawUAString field suggests that the browser's User Agent string is generated by a custom test harness.
Device and OS: The benchmark is run on a desktop with Mac OS X 10.15.7.

Library/Dependencies

None of the provided code snippets use any external libraries or dependencies, other than the built-in JavaScript Array methods.

Special JS Features/Syntax

There are no special JavaScript features or syntax used in this benchmark beyond the standard array operations and conditional statements (e.g., for, let, const).

LLMs can make mistakes. Check important info.

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

**Benchmark Overview**

The benchmark measures the performance of two JavaScript operations on large arrays: `unshift` and `push + reverse`. The test cases create a small initial array with 10 elements and then either use `unshift` to add 100,000 elements from scratch or use `push` followed by `reverse` to add the same amount of elements in reverse order.

**Approaches Compared**

1. **`unshift`**: This operation adds an element to the end of the array without shifting existing elements. It's a relatively simple and efficient operation.
2. **`push + reverse`**: This approach uses `push` to add elements to the end of the array, followed by `reverse` to rearrange the elements in reverse order.

**Pros and Cons**

* **`unshift`**:
	+ Pros: Simple, fast, and efficient ( O(1) average case).
	+ Cons: May not be suitable for arrays with many existing elements, as it can lead to fragmentation.
* **`push + reverse`**:
	+ Pros: Can handle large arrays with many existing elements, as `push` doesn't affect the indexing of existing elements. Also, `reverse` can take advantage of JavaScript's caching mechanisms for reversals.
	+ Cons: More complex and slower than `unshift`, especially for small to medium-sized arrays.

**Other Considerations**

* **Array size**: The benchmark creates a large array with 100,000 elements. This is likely done to minimize the impact of array resizing or reallocation, which can be expensive operations.
* **JavaScript engine**: The benchmark is run on Chrome 123, which may not be the most recent version. Additionally, the `RawUAString` field suggests that the browser's User Agent string is generated by a custom test harness.
* **Device and OS**: The benchmark is run on a desktop with Mac OS X 10.15.7.

**Library/Dependencies**

None of the provided code snippets use any external libraries or dependencies, other than the built-in JavaScript `Array` methods.

**Special JS Features/Syntax**

There are no special JavaScript features or syntax used in this benchmark beyond the standard array operations and conditional statements (e.g., `for`, `let`, `const`).

Related benchmarks:

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

Comparing performance of: unshift vs push + reverse

Created: 2 years ago by: Guest

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