Benchmark: Prepand to array

HTML Preparation code:

<script src='https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js'></script>

Script Preparation code:

var oldArray = [];
for (var i = 1; i<4000; i++) {
  oldArray.push({id: i, name: "Name "+ i });
}

Tests:

concat
var newArray = [{id: 0, name: "All"}].concat(oldArray);
unshift
var newArray = oldArray.unshift({id: 0, name: "All"});

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
concat
unshift

Fastest: N/A

Slowest: N/A

Latest run results:

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Autogenerated LLM Summary (model llama3.1:latest, generated one year ago):

LLMs can make mistakes. Check important info.

Let's break down what's being tested and compared in this benchmark.

**Benchmark Overview**

The benchmark is called "Prepare to array" and its purpose is to compare the performance of two different ways to add an element at the beginning of an existing JavaScript array.

**Test Cases**

There are two test cases:

1. **concat**: This test case uses the `concat()` method to add a new element at the beginning of the `oldArray`. The code snippet for this test case is: `var newArray = [{id: 0, name: "All"}].concat(oldArray);`.
2. **unshift**: This test case uses the `unshift()` method to add a new element at the beginning of the `oldArray`. The code snippet for this test case is: `var newArray = oldArray.unshift({id: 0, name: "All"});`.

**Library Used**

In the benchmark preparation code, jQuery library is loaded. However, it's not directly used in either of the test cases.

**Special JS Feature or Syntax**

There are no special JavaScript features or syntax being tested here. Both `concat()` and `unshift()` methods are standard array methods in JavaScript.

**Pros and Cons of Different Approaches**

In this benchmark, we're comparing two different approaches to add an element at the beginning of an existing array:

* **concat():** This method creates a new array by concatenating the original array with a new element. It's generally slower than `unshift()` because it creates a new array and copies all elements from the original array.
* **unshift():** This method adds one or more elements at the beginning of an existing array, effectively shifting all other elements down. It's generally faster than `concat()` since it only requires updating the array length and shifting the elements.

**Other Alternatives**

While not being tested in this specific benchmark, there are other ways to add elements at the beginning of a JavaScript array:

* Using the spread operator (`[...array, newElement]`)
* Using array destructuring (`array.unshift(newElement)`, although this is essentially equivalent to `unshift()`)

**Considerations**

When choosing between `concat()` and `unshift()`, consider the following:

* If you need to add multiple elements at the beginning of an array, use `unshift()` for better performance.
* If you're working with large arrays or need to maintain a specific order, using `concat()` might be more suitable since it creates a new array without modifying the original one.

Keep in mind that these results are highly dependent on the specific browser and environment being tested.

Related benchmarks:

Prepand to array (version: 0)

Comparing performance of: concat vs unshift

Created: 7 years ago by: Guest

Jump to the latest result

concat

unshift

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

Autogenerated LLM Summary (model llama3.1:latest, generated one year ago):