Benchmark: For loop comparison

Script Preparation code:

var arr = [];
var n = 0;
var i;
var l;
for (i = 0; i < 1000; i++) {
  arr[i] = i;
}

Tests:

Normal
for (i = 0; i < arr.length; i++) { n += arr[i]; }
Extra assignment
for (i = 0, l = arr.length; i < l; i++) { n += arr[i]; }
Assignment before the loop
var l = arr.length; for (i = 0; i < l; i++) { n += arr[i]; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Normal
Extra assignment
Assignment before the loop

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

This benchmark does not have any results yet. Be the first one to run it!

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

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks.

**Benchmark Overview**

The benchmark, called "For loop comparison," tests three different approaches for iterating over an array in a `for` loop: normal iteration, extra assignment (i.e., using both variables `l` and `i` in the loop condition), and assignment before the loop. The goal is to compare the performance of these three approaches.

**Benchmark Definition JSON**

The benchmark definition JSON contains four essential pieces of information:

1. **Name**: A unique identifier for the benchmark.
2. **Description**: A brief description of the benchmark (currently empty).
3. **Script Preparation Code**: A JavaScript code snippet that initializes variables before running the test case. In this case, it creates an array `arr` and initializes variables `n`, `i`, and `l`.
4. **Html Preparation Code**: Currently empty.

**Test Cases**

There are three individual test cases:

1. **Normal**: Tests the standard way of iterating over an array in a `for` loop.
2. **Extra assignment**: Tests using both variables `l` and `i` in the loop condition.
3. **Assignment before the loop**: Tests assigning `l` (the length of the array) before the loop.

**Options Compared**

The benchmark compares the performance of three different approaches:

1. **Normal iteration**: Using `for (var i = 0; i < arr.length; i++) { ... }`
2. **Extra assignment**: Using `for (var i = 0, var l = arr.length; i < l; i++) { ... }`
3. **Assignment before the loop**: Using `var l = arr.length; for (var i = 0; i < l; i++) { ... }`

**Pros and Cons**

Here are some pros and cons of each approach:

1. **Normal iteration**:
	* Pros: Simple, easy to read, and understand.
	* Cons: May lead to slower performance due to the extra operation of incrementing `i`.
2. **Extra assignment**:
	* Pros: Reduces the number of increments needed for `l`, potentially improving performance.
	* Cons: Requires using two variables in the loop condition, which might make the code harder to read and understand.
3. **Assignment before the loop**:
	* Pros: Can improve performance by reducing the number of increments needed for `l`.
	* Cons: May lead to code that is less readable and maintainable due to variable scope.

**Library Usage**

There are no libraries used in this benchmark. However, it's worth noting that using libraries can affect the outcome of microbenchmarks, as they may introduce additional overhead or optimizations that are not relevant to the specific test case.

**Special JS Features/Syntax**

This benchmark does not use any special JavaScript features or syntax beyond the standard `for` loop and variable declarations.

Related benchmarks:

For loop comparison (version: 0)

Comparing performance of: Normal vs Extra assignment vs Assignment before the loop

Created: 9 years ago by: Guest

Jump to the latest result

Normal

Extra assignment

Assignment before the loop

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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