Benchmark: for (reverse with length) vs for with small array

Script Preparation code:

var array = new Array(100);

Tests:

for
for (var i = 0; i < array.length; i++) { array[i]; }
for (reverse with length)
var length = array.length; for (var i = length; --i >= 0;) { array[i]; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for
for (reverse with length)

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/97.0.4692.71 Safari/537.36

Browser/OS: Chrome 97 on Windows

View result in a separate tab

Test name	Executions per second
for	48622.1 Ops/sec
for (reverse with length)	91895.0 Ops/sec

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

LLMs can make mistakes. Check important info.

I'll break down the explanation into smaller sections to make it easier to understand.

**Benchmark Definition and Script Preparation Code**

The benchmark definition is a JSON object that contains metadata about the test case, including its name and description. The script preparation code is a JavaScript snippet that creates an array of length 100 before running the benchmark tests. This ensures that both test cases start with the same initial state.

**Individual Test Cases**

There are two individual test cases:

1. **"for"`**: This test case measures the execution time of a traditional `for` loop that iterates over the array using its length.
2. **"for (reverse with length)"**: This test case measures the execution time of a modified `for` loop that uses the array's length to iterate in reverse order.

**Library and Special JS Feature**

Both test cases use a library: `Array.prototype.forEach()` is not explicitly mentioned, but the syntax used is very similar. However, it is safe to assume that some sort of optimized version of the `forEach` method is being used, as modern JavaScript engines like V8 (used in Chrome) often provide optimized implementations for common array methods.

There are no special JS features or syntaxes being tested in these benchmark cases.

**Options Compared**

The two test cases compare the performance of:

1. Traditional `for` loop with manual index management (`array.length`)
2. Modified `for` loop with reverse iteration using the array's length

**Pros and Cons of Different Approaches**

Here are some pros and cons of each approach:

* **Traditional `for` loop**: Advantages:
	+ Simple to implement
	+ Easy to understand
	+ Works well for small arrays
Disadvantages:
	+ May have slower performance due to manual index management
	+ Can lead to off-by-one errors if not implemented carefully
* **Modified `for` loop with reverse iteration**: Advantages:
	+ Often faster than traditional `for` loops due to optimized implementations by modern JavaScript engines
	+ Reduces the chance of off-by-one errors
Disadvantages:
	+ More complex to implement
	+ May require careful consideration of edge cases

**Other Considerations**

When interpreting these benchmark results, consider the following:

* Modern JavaScript engines like V8 often provide optimized implementations for common array methods, which can affect the performance difference between traditional and modified `for` loops.
* The size of the array (100 in this case) may not be representative of real-world scenarios, where arrays are often smaller or larger.

**Alternatives**

If you want to explore more benchmark cases, here are some alternatives:

1. **`forEach()` vs `map()`**: Compare the performance of using `forEach()` and `map()` for array iteration.
2. **Traditional `for` loop vs `while` loop**: Compare the performance of traditional `for` loops with manual index management versus `while` loops.
3. **Object iteration vs Array iteration**: Explore the performance differences between iterating over objects using `forEach()` or `for...in`, and arrays using `forEach()` or a traditional `for` loop.

Keep in mind that benchmarking JavaScript code can be complex, as it depends on various factors like engine versions, hardware configurations, and other external influences.

Related benchmarks:

for (reverse with length) vs for with small array (version: 0)

Comparing performance of: for vs for (reverse with length)

Created: 2 years ago by: Guest

Jump to the latest result

for

for (reverse with length)

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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