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`Array.slice(-1)[0]` vs `Array[Array.length]`
(version: 0)
Comparing performance of:
`Array.slice(-1)[0]` vs `Array[Array.length]`
Created:
6 years ago
by:
Guest
Jump to the latest result
Script Preparation code:
var arr = Array.from(Array(100).keys());
Tests:
`Array.slice(-1)[0]`
arr.slice(-1)[0];
`Array[Array.length]`
arr[arr.length-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.slice(-1)[0]`
`Array[Array.length]`
Fastest:
N/A
Slowest:
N/A
Latest run results:
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Autogenerated LLM Summary
(model
llama3.2:3b
, generated one year ago):
Let's break down the provided benchmark and explain what's being tested, compared, and analyzed. **Benchmark Overview** The benchmark is comparing two ways to access the last element of an array in JavaScript: `Array.slice(-1)[0]` and `arr[arr.length-1]`. **Script Preparation Code** Before running each test case, the script preparation code creates a large array (`arr`) with 100 elements, using the following line: ```javascript var arr = Array.from(Array(100).keys()); ``` This creates an array of numbers from 0 to 99. **Benchmark Definition** The benchmark definition is a JSON object that contains two test cases: 1. `Array.slice(-1)[0];`: This test case measures the performance of accessing the last element of the array using the `slice()` method and indexing `[0]`. 2. `arr[arr.length-1];`: This test case measures the performance of accessing the last element of the array directly using indexing `[arr.length-1]`. **Library/Features Used** In this benchmark, no libraries or special JavaScript features are used. **Options Compared** The two options being compared are: 1. Using `Array.slice(-1)[0]`: This method creates a new slice of the original array with only one element (the last one), and then accesses that element using `[0]`. This approach is often considered more explicit and safer, but may incur a performance overhead due to the creation of a new slice. 2. Using `arr[arr.length-1]`: This method directly indexes into the original array to access the last element. This approach is often considered faster and more efficient, as it avoids creating unnecessary intermediate data structures. **Pros and Cons** Here are some pros and cons of each approach: * **Using `Array.slice(-1)[0]`**: + Pros: More explicit and safer, as it avoids modifying the original array. + Cons: May incur a performance overhead due to the creation of a new slice. * **Using `arr[arr.length-1]`**: + Pros: Faster and more efficient, as it directly indexes into the original array. + Cons: Less explicit and safer, as it relies on indexing into the array. **Other Alternatives** If you need to access the last element of an array in JavaScript, other alternatives include: * Using `arr[arr.length - 1]`: This is a more concise way to access the last element using direct indexing. * Using a library like Lodash, which provides a function called `last()` that can be used to access the last element of an array. **Benchmark Result** The latest benchmark result shows the performance metrics for both test cases: | Test Name | ExecutionsPerSecond | | --- | --- | | `Array.slice(-1)[0]` | 10328980.0 | | `arr[arr.length-1]` | 7843144.0 | This suggests that accessing the last element using `arr[arr.length-1]` is faster than using `Array.slice(-1)[0]`. However, the actual performance difference may vary depending on the specific use case and JavaScript engine being used. I hope this explanation helps!
Related benchmarks:
`Array.slice(-1)[0]` vs `Array[Array.length]` for 10000 length
slice vs length-1
Test slice vs array.length accessing last element
`array.slice(-1)[0]` vs `array[array.length - 1]`
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