Benchmark: Slice vs shift and pop

Script Preparation code:

var array = Array(200).fill(0)

Tests:

slice
array = array.slice(1, -1);
shift and pop
array.shift(); array.pop();

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
slice
shift and pop

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36 Edg/131.0.0.0

Browser/OS: Chrome 131 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
slice	7886595.0 Ops/sec
shift and pop	21164278.0 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated one year ago):

LLMs can make mistakes. Check important info.

The benchmark named **"Slice vs shift and pop"** compares the performance of two different methods for removing two items from the start of an array in JavaScript. The key methods being tested are:

1. **Array.prototype.slice()**
   - **Test Case:** `array = array.slice(1, -1);`
   - This method returns a shallow copy of a portion of an array into a new array object. In this case, it slices the original array starting from the second element (index 1) and ending one element before the last (index -1).
   - **Pros:** 
     - It creates a new array, so the original is unchanged.
     - Functional programming style can lead to clearer and more maintainable code by avoiding side effects.
   - **Cons:** 
     - It can be less efficient in terms of memory usage since it creates a new array object. This can be significant with larger arrays.
     - The need to copy the remaining elements can lead to increased execution time, especially with larger data sets.
  
2. **Array.prototype.shift() and Array.prototype.pop()**
   - **Test Case:** 
   ```javascript
   array.shift();
   array.pop();
   ```
   - The `shift()` method removes the first element from an array and returns that element, while `pop()` removes the last element and also returns that element. Thus, combining these two will effectively remove the first and last items.
   - **Pros:** 
     - In-place modification means no new array is created, leading to less memory overhead.
     - Generally faster for removing elements from the start (shift) and end (pop) due to fewer operational steps compared to creating a new array.
   - **Cons:** 
     - These methods change the original array, which can lead to side effects if the original data is still needed later in the code.
     - Operations on the beginning of an array can have O(n) complexity since it may require reindexing the subsequent elements.

### Comparative Performance Results:
The benchmark results show:
- **shift and pop:** 21,164,278 executions per second
- **slice:** 7,886,595 executions per second

This indicates that the combination of `shift()` and `pop()` is significantly faster than using `slice()` in this context.

### Other Considerations:
- **Data Setup:** The benchmark initializes an array of 200 elements filled with zeros before the tests are executed, which is essential for consistent measurements.
- **Browser Environment:** The results are executed under Chrome 131 on macOS, emphasizing that performance can vary based on the JavaScript engine and the environment.

### Alternatives and Other Considerations:
Other alternatives for removing items from the beginning of an array could include:
- **Using `splice()`:** However, `splice()` is more versatile and allows for removing elements at any index, but it also modifies the original array and may carry similar performance considerations as `shift()`.
- **Copying arrays in functional paradigms:** Using libraries like Lodash or functional programming approaches can provide additional options but may introduce performance overhead due to the use of the entire library or additional abstractions.
- **Immutable Data Structures:** Libraries like Immutable.js provide data structures that can leverage immutability benefits but at a potential performance cost over native JS arrays.

In conclusion, the choice between these methods should align with both performance requirements and the importance of maintaining immutability within your application's architecture. Understanding the pros and cons is crucial, especially for performance-critical applications or when working with large data sets.

Related benchmarks:

Slice vs shift and pop (version: 1)

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

Comparing performance of: slice vs shift and pop

Created: one year ago by: Guest

Jump to the latest result

slice

shift and pop

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated one year ago):