Benchmark: slice VS splice VS shift: smaller list, copy last half of array

Script Preparation code:

var list = [];
for (var i = 0; i < 1000; i++) {
  list.push(i);
}

Tests:

slice
list.push('slice'); list = list.slice(500);
splice
list.push('splice'); list.splice(0, 500);
shift
list.push('splice'); for (var i = 0; i < 500; i++) { list.shift(); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
slice
splice
shift

Fastest: N/A

Slowest: N/A

Latest run results:

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

LLMs can make mistakes. Check important info.

Let's break down what's being tested in the provided JSON and explain the different approaches, their pros and cons, and other considerations.

**Benchmark Definition:**
The benchmark is testing three ways to extract a subset of an array (or list) from JavaScript:

1. `slice()`: Creates a new copy of the original array with a specified start index.
2. `splice()`: Modifies the original array by removing elements from a specified start index and inserting a new element at that position.
3. `shift()`: Removes the first element from the array and returns it.

**Description:**
The benchmark compares the performance of these three approaches on an array of 100,000 elements, specifically when extracting the last half of the array (500 elements). The results show that `splice` is significantly faster than `slice`, which creates a copy of the entire array. `shift()` is also slower due to its overhead.

**Options Compared:**
The benchmark compares the performance of three different approaches:

1. `slice()`: Creates a new copy of the original array.
	* Pros: Efficient and predictable, as it doesn't modify the original array.
	* Cons: Can be slower than `splice` for large arrays due to its overhead.
2. `splice()`: Modifies the original array by removing elements from the start index and inserting a new element at that position.
	* Pros: Often faster than `slice`, especially for large arrays, as it modifies the original data structure.
	* Cons: Can be slower than `slice` if the array is small, and modifying the original array can have unintended consequences.
3. `shift()`: Removes the first element from the array and returns it.
	* Pros: Fast and efficient for removing elements from the beginning of an array.
	* Cons: Slower than `splice` when extracting a subset of elements, as it involves multiple operations.

**Library and Special JS Feature:**
None mentioned in this benchmark. However, note that some JavaScript engines might use specialized optimizations or features (like SIMD instructions) for certain functions, which could affect performance.

**Other Considerations:**

* The benchmark uses a large array size to demonstrate the performance differences between these approaches.
* The results assume a relatively modern browser version (Chrome 111).
* Other factors like memory allocation and garbage collection might influence performance in real-world scenarios.

**Alternatives:**
If you need to extract elements from an array, consider using:

1. `filter()`: Creates a new array with elements that pass a test.
2. `map()`: Creates a new array by applying a transformation function to each element.
3. Array.prototype.reduce(): A more complex approach for reducing arrays to a single value.

Keep in mind that these alternatives might have different performance characteristics and use cases compared to the original three approaches tested in this benchmark.

Related benchmarks:

slice VS splice VS shift: smaller list, copy last half of array (version: 0)

100k list splice and shift win, they mutate list slice loose, it creates a copy of list 7.5x slower

Comparing performance of: slice vs splice vs shift

Created: 3 years ago by: Guest

Jump to the latest result

slice

splice

shift

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):