Benchmark: shift vs slice (copy array)

Script Preparation code:

const array = []
for (let i = 0; i < 1e3; ++i) array.push(i)

Tests:

shift
array.shift()
slice
array.slice(1)
manual
for (let i = 1; i < array.length; ++i) array[i - 1] = array[i] array.pop()

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
shift
slice
manual

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 4 months ago)

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 18_7 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/18.7.2 Mobile/15E148 Safari/604.1

Browser/OS: Mobile Safari 18 on iOS 18.7

View result in a separate tab

Test name	Executions per second
shift	62002944.0 Ops/sec
slice	19958484.0 Ops/sec
manual	210946320.0 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated 6 months ago):

LLMs can make mistakes. Check important info.

The benchmark in question compares three different methods for removing the first element from an array in JavaScript, specifically testing their performance. The methods being analyzed are:

1. **`array.shift()`**
2. **`array.slice(1)`**
3. **Manual shifting via a loop and `array.pop()`**

### Benchmark Options and Definitions

#### 1. **`array.shift()`**
- **Description**: This built-in JavaScript method removes the first element from an array and returns that element. The indices of the remaining elements are updated accordingly.
- **Pros**: 
  - Simple to use and read; code is very intuitive for understanding.
  - Built-in function, so there's no need for additional coding or logic.
- **Cons**:
  - This operation can have performance overhead, especially for large arrays, as it requires shifting all remaining elements down by one index.
  
#### 2. **`array.slice(1)`**
- **Description**: This method creates a new array that is a shallow copy of a portion of the original array, starting from index 1 to the end of the array.
- **Pros**:
  - Creates a new array that can be easily manipulated.
  - Doesn’t mutate the original array, which can be useful in functional programming paradigms.
- **Cons**:
  - Less efficient because it creates a new array, resulting in additional memory allocation.
  - Can lead to increased garbage collection overhead, particularly with larger arrays.

#### 3. **Manual shifting via loop and `array.pop()`**
- **Description**: This approach manually shifts the elements left by iterating through the array, copying subsequent elements to the previous index, and then using `array.pop()` to remove the last element.
- **Pros**:
  - Performance optimization by eliminating the need for built-in operations that handle shifting elements automatically.
  - Can be tuned for specific use cases.
- **Cons**:
  - More complex to implement, which might lead to code that is harder to maintain and understand.
  - The manual loop could still have similar overhead issues as `shift()` due to the nature of moving elements.

### Benchmark Results
The results from the benchmark revealed the following performance metrics for `ExecutionsPerSecond`:

- **Manual Shift**: 123,381,248 operations/second
- **Shift Method**: 104,622,120 operations/second
- **Slice Method**: 64,401,884 operations/second

This data indicates that the manual approach outperforms both the `shift()` method and `slice()`, highlighting its efficiency for the specific task of removing the first element from an array.

### Additional Considerations and Alternatives
When considering alternatives to these methods, developers might also look into:

- **Array Deconstruction**: While not as performant for large arrays, using spread syntax can succinctly express intent (`const newArray = [...array.slice(1)]`), at the cost of performance.
- **Using a Linked List**: For applications where frequent additions and removals at both ends are required, implementing a linked list could be more efficient. However, this typically requires more complex data handling and isn’t natively supported in JavaScript.

### Conclusion
The benchmark effectively showcases the performance impact of various methods for manipulating arrays in JavaScript, illustrating the trade-offs between readability, performance, and mutability. As such, developers should consider their specific needs and context (maintainability vs. performance) when choosing an approach to remove elements from arrays.

Related benchmarks:

shift vs slice (copy array) (version: 1)

Comparing performance of: shift vs slice vs manual

Created: 6 months ago by: Guest

Jump to the latest result

shift

slice

manual

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated 6 months ago):