Benchmark: length -1 vs last

HTML Preparation code:

<script src='https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.5/lodash.min.js'></script>

Script Preparation code:

var array = ['banana', 'sausage', 'jesus', 'sausage', 'jesus', 'sausage', 'jesus', 'sausage', 'jesus', 'sausage', 'jesus', 'sausage', 'jesus']

Tests:

length -1
array[array.length -1]
last
_.last(array)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
length -1
last

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/133.0.0.0 Safari/537.36

Browser/OS: Chrome 133 on Windows

View result in a separate tab

Test name	Executions per second
length -1	197659200.0 Ops/sec
last	189393936.0 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

LLMs can make mistakes. Check important info.

I'll explain the JavaScript microbenchmark test case provided by MeasureThat.net.

**What is tested?**

The benchmark measures the performance difference between two approaches to access the last element of an array:

1. `array[array.length - 1]`
2. `_.last(array)` (using Lodash library)

**Options compared:**

* Direct array indexing with subtraction (`array[array.length - 1]`)
* Using a dedicated function from the Lodash library (`_.last(array)`) to access the last element of an array

**Pros and Cons:**

* **Direct array indexing with subtraction**:
	+ Pros:
		- Simple, direct approach
		- Typically fast since it only involves arithmetic operations
	+ Cons:
		- May be slower for larger arrays due to the need for arithmetic operations
		- May require more memory accesses (if the array is very large)
* **Using _.last(array)**:
	+ Pros:
		- Often faster, especially for large arrays, since it's a specialized function optimized by Lodash
		- Can be more readable and maintainable for complex cases where subtraction would be cumbersome
	+ Cons:
		- Requires including the Lodash library, which may add extra overhead
		- May not be suitable for very small arrays where the overhead of the function call outweighs any benefits

**Lodash library:**

The `_.last(array)` function is part of the Lodash library, a popular JavaScript utility library. It's designed to provide a set of functions for common tasks like array manipulation, string formatting, and more. In this case, `_.last(array)` returns the last element of the input array.

**Other considerations:**

* The choice between direct indexing with subtraction and using _.last() may depend on the specific use case, personal preference, or performance requirements.
* For very small arrays (e.g., fewer than 10 elements), direct indexing might be faster due to reduced overhead from function calls.
* As arrays grow in size, the performance difference between these approaches becomes more significant.

**Other alternatives:**

If you prefer not to use Lodash, you can use other libraries or built-in methods like `pop()` or `slice()`, but keep in mind that they might not be as optimized for array access as _.last().

Here's an example of how you could implement direct indexing with subtraction without using a library:
```javascript
function getLastElement(array) {
  return array[array.length - 1];
}
```
Alternatively, if you need to access the last element in multiple places, it might be worth considering creating a small utility function or even a wrapper around an optimized method like `pop()`.

Related benchmarks:

length -1 vs last (version: 0)

Comparing performance of: length -1 vs last

Created: 6 years ago by: Guest

Jump to the latest result

length -1

last

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):