Benchmark: Array.Prototype.at vs index (negative)

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>

Previous results

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

View result in a separate tab

Test name	Executions per second
Array.at()	183893520.0 Ops/sec
Index	64737420.0 Ops/sec

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

LLMs can make mistakes. Check important info.

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.

Related benchmarks:

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

Jump to the latest result

Array.at()

Index

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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