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]; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Normal
Extra assignment

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/119.0.0.0 Safari/537.36

Browser/OS: Chrome 119 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Normal	4094.6 Ops/sec
Extra assignment	4187.5 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what is being tested.

**Benchmark Overview**

The benchmark compares the performance of two for loop approaches: one with an explicit increment (`i++`) and another with a separate variable assignment (`l = arr.length`).

**Options Compared**

There are two main options being compared:

1. **Explicit Increment**: `for (i = 0; i < arr.length; i++) { n += arr[i]; }`
	* This approach uses an explicit increment to iterate through the array, where `i` is incremented by 1 at the end of each iteration.
2. **Extra Assignment**: `for (i = 0, l = arr.length; i < l; i++) { n += arr[i]; }`
	* This approach uses a separate variable assignment to get the length of the array (`l`) and then uses it as the loop condition.

**Pros and Cons**

1. **Explicit Increment**:
	* Pros: Simple, intuitive, and easy to understand.
	* Cons: May lead to unnecessary increments or errors if not used carefully.
2. **Extra Assignment**:
	* Pros: Can be more efficient in some cases, as it avoids the need for an explicit increment operation.
	* Cons: May be less intuitive or harder to read, especially for beginners.

**Other Considerations**

1. **Variable Naming**: Both approaches use variable names that are not very descriptive (e.g., `i`, `l`). Using more descriptive names can make the code easier to understand and maintain.
2. **Array Length**: The benchmark uses an array of length 1000, which may be too small for some browsers or systems. Increasing the array size may provide a better representation of real-world performance.

**Library Usage**

There is no library usage in this benchmark.

**Special JS Features/Syntax**

None mentioned.

**Alternatives**

For those interested in exploring other options, here are a few alternatives:

1. **While Loop**: Use a `while` loop instead of a for loop to iterate through the array: `let i = 0; while (i < arr.length) { n += arr[i]; i++; }`
2. **Array.prototype.forEach()**: Use the `forEach()` method provided by arrays, which iterates through each element and provides an implicit increment operation.
```javascript
arr.forEach((element) => {
  n += element;
});
```

These alternatives may provide different performance characteristics or trade-offs in terms of code readability and maintainability.

Related benchmarks:

For loop comparison (version: 3)

Comparing performance of: Normal vs Extra assignment

Created: 9 years ago by: Registered User

Jump to the latest result

Normal

Extra assignment

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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