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Array.Prototype.at vs index (negative)
(version: 1)
Measures performance between using arr.at(-1) to access an element in an array and arr[arr.length - 1]
Comparing performance of:
Array.at() vs Index
Created:
one year ago
by:
Guest
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Tests:
Array.at()
const arr = ['a','b', 1, 2, true, false]; const val = arr.at(-1);
Index
const arr = ['a','b', 1, 2, true, false]; const val = arr[arr.lenght - 1];
Rendered benchmark preparation results:
Suite status:
<idle, ready to run>
Run tests (2)
Previous results
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Test case name
Result
Array.at()
Index
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/135.0.0.0 Safari/537.36
Browser/OS:
Chrome 135 on Mac OS X 10.15.7
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Embed Benchmark Result
<iframe src="https://measurethat.net/Embed?id=602482" width="100%" height="500px"></iframe>
Array.at()
183.9M/s
Index
64.7M/s
View exact numbers
Test name
Executions per second
✓
Array.at()
183,893,520 Ops/sec
Index
64,737,420 Ops/sec
Autogenerated LLM Summary
(model
gpt-4o-mini
, generated one year ago):
The provided benchmark measures the performance of two methods for accessing elements in a JavaScript array: the `Array.prototype.at` method and the traditional index-based access method. Specifically, it compares `arr.at(-1)`, which retrieves the last element of the array, with `arr[arr.length - 1]`, which achieves the same result using length-based indexing. ### Options Being Compared 1. **Array.at() method**: - **Syntax**: `arr.at(-1)` - **Description**: The `Array.prototype.at()` method allows for accessing elements in an array using a relative index. When passing a negative index, it counts back from the end of the array, making it an intuitive choice for obtaining the last element. - **Pros**: - Improved readability: The code clearly indicates that it is accessing a specific array position relative to the end. - Fewer chances for off-by-one errors, especially with negative indices. - **Cons**: - Slightly less performant than indexed access in some cases (as observed in this benchmark), as it may involve additional function call overhead. 2. **Index-based access**: - **Syntax**: `arr[arr.length - 1]` - **Description**: This method retrieves the last element by manually calculating the index based on the array's length. - **Pros**: - Simple and widely understood by all JavaScript developers, as it has been the traditional means of indexing arrays. - Potentially faster than using the `Array.at()` method, as it operates directly with indices without the overhead of a function call. - **Cons**: - Can lead to off-by-one errors if the developer doesn’t manage the index calculation correctly. - Less readable for someone unfamiliar with the specific behavior of indexing arrays in JavaScript, particularly with negative indices. ### Benchmark Results The benchmark results showcase the performance measured in executions per second: - **Array.at()**: 63,111,436 executions per second - **Index access**: 26,306,806 executions per second These results indicate that using the `Array.at()` method outperforms index-based access significantly in this particular test case. ### Considerations - **Performance**: While performance may vary based on the browser and JavaScript engine optimization strategies, modern engines may optimize different approaches differently. - **Maintainability**: Code readability can be an essential factor for long-term project maintenance. Choosing methods that enhance clarity can benefit collaboration and debugging. - **Browser Compatibility**: While `Array.at()` is supported in modern browsers, legacy environments may not support this newer method, making index-based access more universal. It's critical to evaluate the target environment when deciding on which access method to use. ### Alternatives Other alternatives to these methods do exist when considering array access in JavaScript: - **Using a for loop or `forEach`**: While not as direct for accessing a single element, these methods can be employed if the need to access multiple elements arises. - **Using destructuring assignment**: This can be useful if specific elements are needed, although it wouldn't be optimal for accessing the last element directly. In conclusion, the benchmark examines the performance trade-offs between using `Array.at()` and traditional index-based array access. Developers should consider factors like performance, readability, and browser compatibility when choosing which method to implement in their projects.
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