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shift vs slice (copy array)
(version: 1)
Comparing performance of:
shift vs slice vs manual
Created:
10 months ago
by:
Guest
Go to the latest result
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>
Run tests (3)
Previous results
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Test case name
Result
shift
slice
manual
Fastest:
N/A
Slowest:
N/A
Latest run results:
Run details:
(Test run date:
7 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
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Embed Benchmark Result
<iframe src="https://measurethat.net/Embed?id=622442" width="100%" height="500px"></iframe>
manual
210.9M/s
shift
62.0M/s
slice
20.0M/s
View exact numbers
Test name
Executions per second
✓
manual
210,946,320 Ops/sec
shift
62,002,944 Ops/sec
slice
19,958,484 Ops/sec
Autogenerated LLM Summary
(model
gpt-4o-mini
, generated 10 months ago):
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.
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