Benchmark: for/for len - MeasureThat.net

Script Preparation code:

var array = new Array(10000);
for (let i = 0; i < array.length; i++) {
  array[i] = i;
}

Tests:

for len
let sum = 0; for (let i = 0, len = array.length; i < len; i++) { sum += array[i]; }
for
let sum = 0; for (let i = 0; i < array.length; i++) { sum += array[i]; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for len
for

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/103.0.0.0 Safari/537.36

Browser/OS: Chrome 103 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
for len	1834.2 Ops/sec
for	943.1 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the provided benchmarking scenario.

**Benchmark Test Case**

The test case is designed to measure the performance of JavaScript for loops with different variable declarations and loop conditions. Specifically, it tests two approaches:

1. `for (let i = 0, len = array.length; i < len; i++)`
2. `for (let i = 0; i < array.length; i++)`

**What's being tested?**

The benchmark is testing the performance of these two for loop variants by measuring the number of executions per second on a given JavaScript engine.

**Options compared:**

* **Variable declaration:** In both loops, the variable `i` is declared using the `let` keyword. However, in one loop, `len` is assigned before the loop condition (`i < len`). This approach is considered more efficient than declaring `i` and then assigning `len` inside the loop.
* **Loop condition:** The first loop uses a conditional expression to assign both values (`i` and `len`) at once. In contrast, the second loop declares `i` without an initial value and assigns `len` separately.

**Pros and Cons:**

1. **for (let i = 0, len = array.length; i < len; i++)**
	* Pros:
		+ More efficient since `len` is assigned before the loop condition.
	* Cons:
		+ Less intuitive for some developers who are not familiar with this syntax.
2. **for (let i = 0; i < array.length; i++)**
	* Pros:
		+ More intuitive and widely recognized syntax.
	* Cons:
		+ Less efficient since `len` is assigned separately.

**Library and its purpose:**

The provided benchmarking code uses the built-in JavaScript `Array` class, which provides a way to create arrays and perform operations on them. The array is used as the input data for both loops.

There are no external libraries mentioned in the provided benchmarking code.

**Special JS feature or syntax:**

None of the test cases use any special JavaScript features or syntax beyond what's typically expected from modern JavaScript engines.

**Other alternatives:**

If you wanted to run this benchmark, you could implement similar tests using other programming languages that support for loops. Some alternative approaches might include:

* Using Python (with its built-in `range` function) and measuring the performance of a similar loop structure.
* Implementing the test case in C++ (or another low-level language) to compare the performance of compiled vs. interpreted code.

However, since this benchmark is designed specifically for JavaScript, using other languages might not provide meaningful insights into the engine's behavior.

I hope this explanation helps!

Related benchmarks:

for/for len (version: 0)

Comparing performance of: for len vs for

Created: 2 years ago by: Guest

Jump to the latest result

for len

for

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):