Benchmark: Iterator vs Index for loop (global sum)

Script Preparation code:

var arr = [];
for(let i = 0; i < 10000; i++) {
  arr.push(Math.random());
}
var arrLength = arr.length;
var sum = 0;

Tests:

Iterator for loop
for(const num of arr) { sum += num; }
Index for loop
for(let i = 0; i < arrLength; i++) { sum += arr[i]; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Iterator for loop
Index for loop

Fastest: N/A

Slowest: N/A

Latest run results:

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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 and explore what's being tested in this particular benchmark.

**What is being tested?**

The provided JSON represents two individual test cases that compare the performance of different approaches to iterate over an array in JavaScript:

1. **Iterator for loop**: This approach uses a `for...of` loop, which creates an iterator object from the array and allows it to be iterated over without exposing its underlying implementation.
2. **Index for loop**: This approach uses a traditional `for` loop with an index variable (`i`) to iterate over the array.

**Options compared**

The two approaches are being compared in terms of their performance, measured by the number of executions per second.

**Pros and Cons:**

1. **Iterator for loop**
	* Pros:
		+ Can be more memory-efficient since it doesn't require creating a separate index variable.
		+ Can be faster due to reduced overhead from indexing operations.
	* Cons:
		+ May have slower startup times due to the creation of the iterator object.
2. **Index for loop**
	* Pros:
		+ Typically has better cache locality, which can lead to faster performance.
		+ Often has better support for concurrent execution and parallelization.
	* Cons:
		+ Can be less memory-efficient since it requires creating a separate index variable.
		+ May have slower performance due to indexing operations.

**Library usage**

There is no explicit library used in this benchmark, but the `for...of` loop syntax relies on the JavaScript iterator API, which is part of the ECMAScript standard.

**Special JS feature or syntax**

The test case uses the `for...of` loop syntax, which is a relatively recent addition to the JavaScript language (introduced in ECMAScript 2015). This syntax allows for more concise and expressive iteration over arrays and other iterable objects.

**Other alternatives**

If you're interested in exploring alternative approaches, here are a few options:

1. **Array.prototype.forEach()**: A method that iterates over an array and executes a provided callback function for each element.
2. **Array.prototype.map()**: A method that creates a new array by applying a provided callback function to each element of the original array.
3. **Array.prototype.reduce()**: A method that applies a reduction operation to each element of the array, using a provided callback function.

Keep in mind that these alternatives may not be as performant or memory-efficient as the `for...of` loop syntax used in this benchmark.

Related benchmarks:

Iterator vs Index for loop (global sum) (version: 0)

Comparing performance of: Iterator for loop vs Index for loop

Created: 3 years ago by: Registered User

Jump to the latest result

Iterator for loop

Index for 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):