Benchmark: Spread vs unshift sam

Script Preparation code:

var arr = [];
for (let i = 0; i < 100_000; ++i) {
	arr.push('i: ' + i);
}

Tests:

unshift
arr.unshift('AddedToFront'); const arr2 = arr;
spread
const arr2 = ['AddedToFront', ...arr];

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
unshift
spread

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/123.0.0.0 Safari/537.36

Browser/OS: Chrome 123 on Linux

View result in a separate tab

Test name	Executions per second
unshift	16298.5 Ops/sec
spread	255.3 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.

**Benchmark Overview**

The benchmark compares two ways to add elements to an array: using `unshift()` or using the spread operator (`...`). The test case uses a sample JavaScript array, initialized with 100,000 elements, each containing a string representation of its index. This allows us to measure the performance difference between these two approaches.

**Benchmark Definition**

The benchmark definition is provided in JSON format and consists of two parts:

1. **Script Preparation Code**: This code initializes an empty array `arr` and populates it with 100,000 elements using a `for` loop.
2. **Html Preparation Code**: This field is empty, indicating that no HTML-related preparation is needed for this benchmark.

**Individual Test Cases**

The benchmark consists of two test cases:

1. **unshift**: The first test case measures the performance of adding an element to the beginning of the array using `unshift()`. It executes the line `arr.unshift('AddedToFront');` and assigns the result to a new variable `arr2`.
2. **spread**: The second test case measures the performance of creating a new array by spreading the original array using the spread operator (`...`). It executes the line `const arr2 = ['AddedToFront', ...arr];`.

**Library Used**

In this benchmark, no specific JavaScript library is explicitly mentioned or used.

**Special JS Feature/Syntax**

The use of the spread operator (`...`) in one of the test cases introduces a modern JavaScript feature that was introduced in ECMAScript 2015 (ES6). This syntax allows for creating new arrays by spreading existing arrays or other iterable objects.

**Pros and Cons of Each Approach**

1. **unshift()**:
	* Pros: Simple and straightforward to implement.
	* Cons: Can be slower than using the spread operator, as it involves searching for the beginning of the array and updating the length property.
2. **Spread Operator (`...`)**:
	* Pros: Often faster than `unshift()` due to its ability to create a new array without modifying the original one.
	* Cons: Can be less intuitive to read and understand, especially for older browsers or developers unfamiliar with modern JavaScript syntax.

**Other Alternatives**

If you wanted to use alternative approaches, you could consider:

1. **Array.prototype.push()**: Instead of using `unshift()`, you can push elements onto the end of the array and then reverse it.
2. **Slice() function**: You can create a new array by slicing the original array from the beginning to the specified index.

Here's an example:
```javascript
arr = arr.slice(0, 1).concat(['AddedToFront']);
```
Keep in mind that these alternatives might have different performance characteristics and may not be as efficient as using `unshift()` or the spread operator.

In summary, this benchmark measures the performance difference between two approaches to add elements to an array: using `unshift()` versus the spread operator (`...`). The use of modern JavaScript features like the spread operator introduces a new dimension to benchmarking and highlights the importance of considering performance characteristics when optimizing code.

Related benchmarks:

Spread vs unshift sam (version: 0)

Comparing performance of: unshift vs spread

Created: 2 years ago by: Guest

Jump to the latest result

unshift

spread

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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