Benchmark: Slice vs Splice vs Shift (Large Array)

Script Preparation code:

var array = Array(3000).fill(0)
var itemsToRemove = 1000

Tests:

array.slice()
array = array.slice(2)
array.splice()
array.splice(0, itemsToRemove)
array.shift()
for (let i = 0 ; i < itemsToRemove ; i++) array.shift()

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
array.slice()
array.splice()
array.shift()

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 8 months ago)

User agent: Mozilla/5.0 (X11; Linux x86_64; rv:142.0) Gecko/20100101 Firefox/142.0

Browser/OS: Firefox 142 on Linux

View result in a separate tab

Test name	Executions per second
array.slice()	63761336.0 Ops/sec
array.splice()	23080100.0 Ops/sec
array.shift()	238037.7 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, compared, and their pros and cons.

**Benchmark Overview**

The benchmark compares the performance of three methods to remove 2 items from the beginning of an array:

1. `array.slice(2)`
2. `array.splice(0, 1000)` (removes 1000 elements)
3. `for (let i = 0; i < 1000; i++) array.shift()` (shifts 1000 elements)

**Library and Purpose**

The benchmark uses the `Array` prototype method for all three tests, which is a built-in JavaScript library.

**Special JS Features and Syntax**

None of the test cases use any special JavaScript features or syntax. The focus is on comparing the performance of basic array manipulation methods.

**Comparison of Methods**

1. **`array.slice(2)`**: This method creates a new array with elements from index 2 to the end of the original array. It has a time complexity of O(n), where n is the length of the array.
	* Pros: Efficient and concise way to extract a subset of an array.
	* Cons: Creates a new array, which can lead to increased memory usage.
2. **`array.splice(0, 1000)`**: This method removes elements from the beginning of the array and returns them as an array. It has a time complexity of O(n), where n is the length of the removed elements (in this case, 1000).
	* Pros: Removes elements from the beginning of the array in one operation.
	* Cons: Can be slow if many elements need to be removed, and it modifies the original array.
3. **`for (let i = 0; i < 1000; i++) array.shift()`**: This method uses a loop to shift elements from the beginning of the array. It has a time complexity of O(n), where n is the number of elements shifted.
	* Pros: Does not modify the original array and can be more efficient for smaller arrays or when only shifting a small portion.
	* Cons: Can be slower than `splice` for large arrays, as it involves multiple loop iterations.

**Benchmark Results**

The latest benchmark results show that:

* `array.splice(0, 1000)` is the fastest method, with an average execution time of around 107,759,000 executions per second.
* `array.slice(2)` is slower, with an average execution time of around 118,810,860 executions per second.
* `for (let i = 0; i < 1000; i++) array.shift()` is the slowest method, with an average execution time of around 13,587 executions per second.

**Alternatives**

Other alternatives to these methods include:

* Using `Array.prototype.slice.call()` or `Array.prototype.splice.call()` to avoid creating new objects.
* Using a library like Lodash to optimize array manipulation.
* Using a Just-In-Time (JIT) compiler or optimizing the code for a specific browser/OS combination.

Keep in mind that the performance differences between these methods can be significant, and the choice of method depends on the specific use case and requirements.

Related benchmarks:

Slice vs Splice vs Shift (Large Array) (version: 0)

Compares the speed for removing 2 items from the beginning of an array

Comparing performance of: array.slice() vs array.splice() vs array.shift()

Created: 3 years ago by: Guest

Jump to the latest result

array.slice()

array.splice()

array.shift()

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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