Benchmark: ... & unshift - MeasureThat.net

Script Preparation code:

var number = +prompt('Enter array length')
var arr = new Array(number).fill(10);

Tests:

...
arr = [ 9, ...arr]
unshift
arr.unshift(9)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
...
unshift

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years 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
...	82.0 Ops/sec
unshift	10502.4 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 Definition**

The first section of the benchmark definition represents the test case that will be executed. In this case, two test cases are defined:

1. `arr = [ 9, ...arr]`: This test case creates an array and assigns it to a variable named `arr`. The spread operator (`...`) is used to create a copy of the original array, which is then appended with a new element (in this case, `9`). This operation modifies the original array.
2. `arr.unshift(9)`: This test case creates an empty array and assigns it to a variable named `arr`. The `unshift()` method is then called on the array, passing `9` as an argument. This operation adds `9` as the first element of the array.

**Options Compared**

The two test cases are comparing different approaches to manipulate arrays:

1. Using the spread operator (`...`) to create a copy and append an element.
2. Using the `unshift()` method to add an element at the beginning of the array.

**Pros and Cons**

Here's a brief overview of the pros and cons of each approach:

* **Using the spread operator (`...`)**:
	+ Pros: Creates a new array with a copy of the original elements, which can be useful for immutability.
	+ Cons: May have performance overhead due to the creation of a new array.
* **Using `unshift()`**:
	+ Pros: Modifies the original array in-place, reducing memory allocation and deallocation overhead.
	+ Cons: Can be slower than creating a new array using the spread operator.

**Library and Special JavaScript Features**

Neither of these test cases uses any external libraries or special JavaScript features. They only rely on built-in JavaScript functionality.

**Benchmark Preparation Code**

The preparation code for each test case is provided as part of the benchmark definition:

1. The first test case creates an array with a random length using `new Array(number).fill(10)`.
2. The second test case creates an empty array and assigns it to a variable named `arr`.

**Other Considerations**

When running these benchmarks, it's essential to consider factors such as:

* Cache performance: Both approaches may have different cache behavior, which could affect performance.
* Array resizing: When using the spread operator, JavaScript may need to resize the original array, which can be slower than using `unshift()`.

**Alternatives**

If you're interested in exploring alternative approaches or modifications to these test cases, some possible alternatives include:

1. Using a library like Lodash's `concat` method or Array.prototype.slice() to create a copy of an array.
2. Implementing custom array allocation and deallocation logic to optimize performance.
3. Modifying the benchmark to use different types of arrays (e.g., sparse arrays) or data structures.

Keep in mind that modifying these test cases may require significant changes to the underlying implementation, so it's essential to thoroughly understand the implications before making any modifications.

Related benchmarks:

... & unshift (version: 0)

Comparing performance of: ... vs unshift

Created: 2 years ago by: Guest

Jump to the latest result

...

unshift

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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