Benchmark: Splice vs Spread vs Unshift to insert at beginning of array vs manual

Script Preparation code:

var array = Array.from({ length: 100 }).map((val, i) => i);

Tests:

Splice
var newArray = array.slice(0, 0, 99);
Spread
var newArray = [99, ...array];
Unshift
var newArray = array.unshift(99);
manual
var len=array.length, item=99; while (len) { array[len] = array[len-1]; len--} array[0] = item;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Splice
Spread
Unshift
manual

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 llama3.2:3b, generated one year ago):

LLMs can make mistakes. Check important info.

Let's dive into the explanation of the benchmark.

**Benchmark Purpose:**
The benchmark measures the performance difference between four methods to insert an element at the beginning of an array:

1. `Splice`: Removing and inserting an element at a specific position in an array.
2. `Spread`: Using the spread operator (`...`) to create a new array with the desired elements inserted at the beginning.
3. `Unshift`: Inserting an element at the beginning of an array using the `unshift` method.
4. Manual: Creating a new array by shifting all existing elements to the right and then inserting the desired element.

**Options Compared:**

* **Splice**: Removes and inserts an element at a specific position in the original array, which can be inefficient if not implemented correctly.
* **Spread**: Creates a new array with the desired elements inserted at the beginning using the spread operator. This approach is often faster than `splice` because it avoids modifying the original array.
* **Unshift**: Inserts an element at the beginning of the array by shifting all existing elements to the right, which can be efficient if the array is large and the insertion point is near the end.
* **Manual**: Creates a new array by manually shifting all existing elements to the right and then inserting the desired element. This approach requires more memory allocation and copying than `unshift`, but it avoids modifying the original array.

**Pros and Cons:**

* **Splice**:
	+ Pros: Simple and widely supported, can be used in most situations.
	+ Cons: Can be inefficient if not implemented correctly, modifies the original array.
* **Spread**:
	+ Pros: Fast, efficient, and avoids modifying the original array.
	+ Cons: Only available in modern browsers (IE 11 and later), requires JavaScript engine support for spread syntax.
* **Unshift**:
	+ Pros: Efficient for large arrays with insertion points near the end.
	+ Cons: Requires shifting all existing elements to the right, can be slow if array is very large or has many elements being inserted.
* **Manual**:
	+ Pros: Avoids modifying the original array, can be efficient if array size and insertion point are known.
	+ Cons: Requires more memory allocation and copying than `unshift`, may not be suitable for all use cases.

**Libraries Used:**
None mentioned in the provided benchmark definition. However, some libraries like Lodash (`_.spread`) or Ramda (`R.from_) might be used to implement these benchmarks.

**Special JavaScript Features/Syntax:**

* None mentioned in this benchmark. The only special syntax is the spread operator (`...`), which is a modern JavaScript feature introduced in ECMAScript 2015 (ES6).

**Alternative Approaches:**
Other methods for inserting an element at the beginning of an array could be:

* `concat`: Concatenating an array with a new array containing the desired element.
* Array.prototype.reduce: Using `reduce` to build a new array from scratch, inserting the desired element at the beginning.
* Custom loop or recursive function: Implementing a custom loop or recursive function to insert the desired element at the beginning of the array.

These alternative approaches might be more suitable for certain use cases, but they may also have their own set of pros and cons compared to the methods tested in this benchmark.

Related benchmarks:

Splice vs Spread vs Unshift to insert at beginning of array vs manual (version: 0)

Comparing performance of: Splice vs Spread vs Unshift vs manual

Created: 3 years ago by: Guest

Jump to the latest result

Splice

Spread

Unshift

manual

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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