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:

No previous run results

This benchmark does not have any results yet. Be the first one to run it!

Autogenerated LLM Summary (model gemma2:9b, generated one year ago):

LLMs can make mistakes. Check important info.

This benchmark tests the performance of two different methods for adding an element to the beginning of an array in JavaScript:  `concat()` and `unshift()`.

**Benchmark Breakdown:**

* **Preparation**: The script first creates a large array (`oldArray`) containing 3999 objects, each with an 'id' and 'name' property. This simulates a scenario where you have an existing array of data.

* **Test Cases:**
    * **`concat()`**: This method creates a new array by combining the elements of the original `oldArray` with a single element `{id: 0, name: "All"}`.  
    * **`unshift()`**: This method directly modifies the existing `oldArray` by adding the same element (`{id: 0, name: "All"}`) to its beginning.

**Pros and Cons:**

* **`concat()`:**
    * **Pros:** Returns a new array, leaving the original array unchanged. This is useful when you need to maintain the integrity of the original data.
    * **Cons:** Can be slower than `unshift()` because it creates a new array object.

* **`unshift()`:**
    * **Pros:**  More efficient as it modifies the existing array directly, avoiding unnecessary memory allocation for a new array. 
    * **Cons:** Modifies the original array in place, which may not be desirable if you need to preserve the original data structure.

**Other Considerations:**

* **Array Size:** For very large arrays, `concat()` can become significantly slower due to the overhead of creating a new array.  `unshift()` would likely perform better in these scenarios.
* **Use Case:** The best method depends on your specific use case. If you need to preserve the original array, use `concat()`. If performance is critical and you're okay modifying the original array, use `unshift()`.

**Alternatives:**

The benchmark focuses specifically on adding an element to the beginning of an array. Here are some alternative approaches for working with arrays in JavaScript:

* **`push()`**: Adds an element to the end of an array (modifies the original array).
* **`splice()`**: A versatile method that can insert, remove, or replace elements within an array. It's more complex but offers greater flexibility.
* **Array Methods**: JavaScript provides a rich set of array methods like `map()`, `filter()`, and `reduce()`, which are often more efficient than manually iterating through arrays.

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 gemma2:9b, generated one year ago):