Benchmark: Test slice vs array.length accessing last element

Script Preparation code:

var arr = Array.from(Array(100).keys());

Tests:

Using slice
var last = arr.slice(-1)[0]
Using length
var last = arr[arr.length-1]

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Using slice
Using length

Fastest: N/A

Slowest: N/A

Latest run results:

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Autogenerated LLM Summary (model gemma2:9b, generated one year ago):

LLMs can make mistakes. Check important info.

This benchmark tests two different ways to access the last element of an array in JavaScript:

**Method 1: Using `slice()`**

* **Benchmark Definition:** `var last = arr.slice(-1)[0]`

-  `arr.slice(-1)` creates a new subarray containing only the last element of the original array `arr`.
   - `[0]` accesses the first (and only) element of this subarray, effectively giving you the last element of the original array.

**Method 2: Using `length` property**

* **Benchmark Definition:** `var last = arr[arr.length - 1]`

- `arr.length` returns the number of elements in the array.
   - `arr.length - 1` gives you the index of the last element (remember, arrays are zero-indexed).
   - `arr[arr.length - 1]` accesses the element at that index, which is the last element of the array.

**Pros and Cons:**

* **`slice()`:**
    - **Pros:** More flexible; can extract a range of elements (not just the last one).  Can be used to create a shallow copy of a portion of an array.
    - **Cons:** Creates a new array, which might have a slight performance overhead compared to directly accessing an element.

* **`length` Property:**
    - **Pros:** Generally considered slightly faster than `slice()` for simply accessing the last element. More concise syntax.
    - **Cons:** Less flexible; can't extract ranges of elements like `slice()`.

**Other Considerations:**

The benchmark result shows that `slice()` is slightly faster in this specific case (likely due to optimizations in modern JavaScript engines). However, the difference might not be significant in real-world applications.  The choice between the two methods often comes down to personal preference and code readability.

Let me know if you have any other questions!

Related benchmarks:

Test slice vs array.length accessing last element (version: 0)

Comparing performance of: Using slice vs Using length

Created: 3 years ago by: Guest

Jump to the latest result

Using slice

Using length

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

Autogenerated LLM Summary (model gemma2:9b, generated one year ago):