Benchmark: arr unshift vs double reverse

Script Preparation code:

var arr = [42];

Tests:

unshift
arr.unshift(1);
reverse push reverse
arr.reverse(); arr.push(1);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
unshift
reverse push reverse

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/88.0.4324.192 Safari/537.36

Browser/OS: Chrome 88 on Linux

View result in a separate tab

Test name	Executions per second
unshift	42796.3 Ops/sec
reverse push reverse	2592.7 Ops/sec

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

LLMs can make mistakes. Check important info.

I'd be happy to explain the provided benchmark and its test cases.

**Overview of MeasureThat.net**

MeasureThat.net is a website that allows users to create and run JavaScript microbenchmarks, which are small tests designed to measure the performance of specific pieces of code. The platform aims to provide accurate and reliable results by considering various factors such as device type, operating system, and browser version.

**Benchmark Definition JSON**

The provided benchmark definition JSON contains information about the test case:

* `Name`: "arr unshift vs double reverse"
* `Description`: null
* `Script Preparation Code`: "var arr = [42];" - This code initializes an array with a single element.
* `Html Preparation Code`: null

This script preparation code sets up a simple JavaScript environment by creating an array with a single element. The HTML preparation code is empty, indicating that no additional setup is required for the browser.

**Individual Test Cases**

The test cases are defined in two individual objects:

1. "unshift"
```javascript
Benchmark Definition: arr.unshift(1);
```

This test case measures the performance of the `arr.unshift(1)` statement, which adds an element to the beginning of the array.

2. "reverse push reverse"
```javascript
Benchmark Definition: arr.reverse(); arr.push(1);;
```

This test case measures the performance of two operations in sequence:
	* `arr.reverse()`: reverses the order of the elements in the array.
	* `arr.push(1)`: adds a new element to the end of the array.

**Options Compared**

The benchmark compares two approaches:

1. **`arr.unshift(1)`**: This approach uses the `unshift()` method to add an element to the beginning of the array.
2. **`arr.reverse() + arr.push(1)`**: This approach reverses the order of the elements and then adds a new element at the end using `push()`.

**Pros and Cons**

* **`arr.unshift(1)`**
	+ Pros:
		- O(1) amortized time complexity, making it suitable for large arrays.
		- Typically faster than reversing and pushing.
	+ Cons:
		- Requires extra space to store the added element (the new head of the array).
* **`arr.reverse() + arr.push(1)`**
	+ Pros:
		- More intuitive code structure, making it easier to read and maintain.
	+ Cons:
		- O(n) time complexity for reversing, which can be slower than `unshift()` for large arrays.

**Library Usage**

In the provided benchmark definition, the library used is **`None`**, as there are no external libraries imported or required.

**Special JS Feature/Syntax**

There are no special JavaScript features or syntaxes mentioned in this benchmark. The code examples use standard JavaScript operators and methods.

**Other Alternatives**

For testing performance-related questions like these, other alternatives include:

1. **Benchmarking frameworks**: Libraries like Benchmark.js or WebPageTest can help with setting up and running benchmarks.
2. **Browser-specific profiling tools**: Tools like Chrome DevTools or Firefox Developer Edition provide built-in profiling capabilities for JavaScript performance optimization.
3. **Cloud-based benchmarking services**: Services like JSMonkey or JSPerf allow you to create and run microbenchmarks in a cloud environment.

By understanding the options compared, pros, and cons of each approach, developers can make informed decisions about which method to use when optimizing their code for performance.

Related benchmarks:

arr unshift vs double reverse (version: 0)

Comparing performance of: unshift vs reverse push reverse

Created: 3 years ago by: Guest

Jump to the latest result

unshift

reverse push reverse

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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