Benchmark: reverse & map VS for-loop

Script Preparation code:

var a = [10, 11, 12, 13, 14, 15, 16, 17, 10, 11, 12, 13, 14, 15, 16, 17, 10, 11, 12, 13, 14, 15, 16, 17, 10, 11, 12, 13, 14, 15, 16, 17, 10, 11, 12, 13, 14, 15, 16, 17, 10, 11, 12, 13, 14, 15, 16, 17, 10, 11, 12, 13, 14, 15, 16, 17, 10, 11, 12, 13, 14, 15, 16, 17, 10, 11, 12, 13, 14, 15, 16, 17, 10, 11, 12, 13, 14, 15, 16, 17, 10, 11, 12, 13, 14, 15, 16, 17, 10, 11, 12, 13, 14, 15, 16, 17, 10, 11, 12, 13, 14, 15, 16, 17, 10, 11, 12, 13, 14, 15, 16, 17, 10, 11, 12, 13, 14, 15, 16, 17, 10, 11, 12, 13, 14, 15, 16, 17];

Tests:

for
const b = [] for(let i = a.length-1; i > -1; i--) { b.push(a[i]+1); }
reverse + map
a.reverse().map(a => a+1);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for
reverse + map

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 28 days ago):

LLMs can make mistakes. Check important info.

Measuring JavaScript performance is an essential task, and benchmarks like MeasureThat.net help developers understand the impact of different coding approaches on execution speed.

**Benchmark Definition:**
The benchmark defines two approaches to reverse and map an array: `for-loop` and `reverse + map`. The script preparation code for both approaches is provided. For the `for-loop` approach, a loop starts from the last element (`a.length-1`) and iterates backwards until it reaches `-1`, pushing each element plus one onto a new array (`b`). For the `reverse + map` approach, the original array (`a`) is reversed using the `reverse()` method, followed by mapping over the reversed array to add one to each element.

**Options Compared:**

1. **For-Loop Approach**
	* Pros:
		+ More control over iteration and indexing.
		+ Can be more readable for some developers.
	* Cons:
		+ Can be slower due to the overhead of loop iteration.
		+ May have performance issues if not implemented correctly.
2. **Reverse + Map Approach**
	* Pros:
		+ Often faster due to optimized implementation in JavaScript engines.
		+ Reduces the need for explicit indexing and looping.

**Library Used:**
In this benchmark, no specific library is used. The `reverse()` method is a built-in method of arrays in JavaScript, which reverses the order of elements in an array.

**Special JS Feature/ Syntax:**
The benchmark uses a subtle feature of JavaScript: the fact that arrays are mutable. This allows us to modify the original array (`a`) without creating a new one.

**Pros and Cons Comparison:**

| Approach | Pros | Cons |
| --- | --- | --- |
| For-Loop | More control, readable for some developers | Can be slower, performance issues if not implemented correctly |
| Reverse + Map | Often faster, optimized implementation in JavaScript engines | Less control over iteration, may require additional memory allocation |

**Other Considerations:**

* **Cache locality:** The `for-loop` approach may have better cache locality due to the sequential access of elements. However, this is unlikely to significantly impact performance.
* **Memory allocation:** The `reverse + map` approach requires more memory allocation and deallocation than the `for-loop` approach.

**Alternative Approaches:**

1. **Using `Array.prototype.reduce()`**: Instead of reversing the array and then mapping over it, you can use `Array.prototype.reduce()` to achieve a similar result.
2. **Using a custom iterative implementation**: You could write your own iterative implementation using basic arithmetic operations, which might be more efficient than both approaches.

Keep in mind that these alternative approaches may not necessarily improve performance in all cases and should be evaluated on a case-by-case basis.

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/95.0.4638.69 Safari/537.36

Browser/OS: Chrome 95 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
for	101156.4 Ops/sec
reverse + map	1462893.8 Ops/sec

Related benchmarks:

reverse & map VS for-loop (version: 0)

Comparing performance of: for vs reverse + map

Created: 3 years ago by: Guest

Jump to the latest result

for

reverse + map

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 28 days ago):