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

Script Preparation code:

var arr = Array.from({length: 1000});

Tests:

unshift
var arr2 = []; for (let i = 0; i < arr.length; i++){ arr2.unshift(arr[i]); }
push + reverse
var arr3 = [...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: one year ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/136.0.0.0 Safari/537.36

Browser/OS: Chrome 136 on Windows

View result in a separate tab

Test name	Executions per second
unshift	18893.0 Ops/sec
push + reverse	891880.5 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 analyzed.

**Benchmark Definition**

The benchmark definition consists of two test cases: `unshift` and `push + reverse`. The tests are designed to measure the performance difference between using the `unshift()` method versus a combination of `push()` and `reverse()` methods on an array.

**Test Case 1: unshift**

* Benchmark Definition: `for (let i = 0; i < arr.length; i++) { arr2.unshift(arr[i]); }`
* Purpose: To test the performance of using the `unshift()` method to add elements to the beginning of an array.
* Pros:
	+ Simulates real-world scenario where you need to add new elements to the beginning of an array.
	+ Tests the `unshift()` method's performance in a loop, which is common in many JavaScript applications.
* Cons:
	+ May not accurately reflect the performance of other methods or libraries that optimize insertion at specific indices.

**Test Case 2: push + reverse**

* Benchmark Definition: `var arr3 = [...arr].reverse();`
* Purpose: To test the performance of using the `push()` method to add elements to the end of an array and then reversing the array.
* Pros:
	+ Simulates a common pattern in JavaScript where you need to add new elements to the end of an array and then process them in reverse order.
	+ Tests the performance of the `reverse()` method, which is commonly used for array reversal.
* Cons:
	+ May not accurately reflect the performance of other methods or libraries that optimize insertion at specific indices.

**Library: Array.from()**

In the benchmark definition, `Array.from()` is used to create a new array with a specified length. This method is designed to mimic the behavior of older browsers that don't support the modern `Array.prototype.fill()` method.

* Purpose: To provide a compatible way to create arrays in older browsers or environments where other methods are not supported.
* Pros:
	+ Ensures compatibility across different browser versions and environments.
	+ Simplifies code for developers working with legacy browsers.
* Cons:
	+ May introduce additional overhead due to the use of an older method.

**Special JS feature: Spread operator (`...`)**

In the benchmark definition, the spread operator is used to create a new array by spreading the contents of `arr`. This syntax was introduced in ECMAScript 2015 (ES6) and has since become widely supported.

* Purpose: To provide a concise way to copy arrays or objects in modern JavaScript.
* Pros:
	+ Simplifies code for developers using ES6 features.
	+ Improves readability and maintainability of code.
* Cons:
	+ May not be compatible with older browsers or environments that don't support the spread operator.

**Alternatives**

Other alternatives for testing array insertion performance could include:

1. Using `Array.prototype.fill()` instead of `unshift()`.
2. Testing `splice()` method, which allows you to insert elements at specific indices.
3. Using a library like Lodash or Underscore.js that provides optimized methods for array manipulation.

The provided benchmark is well-designed and covers common scenarios for testing array insertion performance. However, it's essential to note that the results may not be representative of all use cases, and additional tests might be necessary to ensure comprehensive coverage.

Related benchmarks:

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

Comparing performance of: unshift vs push + reverse

Created: 3 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):