Benchmark: for vs for in with index 2

Script Preparation code:

var arr = [];

for (let i = 0; i < 100000; i++)
{
  arr[i] = i*2;
}

Tests:

for
const length = arr.length; for (let i = 0; i < length; i++) { arr[i] = arr[i]*2; }
for..of with index
let index = -1; for (let i of arr) { index++; i = i*2 };

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for
for..of with index

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/72.0.3626.96 Safari/537.36

Browser/OS: Chrome 72 on Windows

View result in a separate tab

Test name	Executions per second
for	40.3 Ops/sec
for..of with index	1498.5 Ops/sec

Autogenerated LLM Summary (model llama3.1:latest, generated one month ago):

LLMs can make mistakes. Check important info.

Let's break down what's being tested in this benchmark.

**The Test Case**

We're comparing two different ways to iterate over an array:

1. `for` loop with index
2. `for...of` loop with index (note: the actual test case uses a `for...of` loop, but it's missing the `.with(index)` part)

Both loops are iterating over an array `arr` with 100,000 elements.

**What's Being Compared**

In this test case, we're comparing the execution speed of two different iteration methods:

* **Method 1:** Traditional `for` loop with index. This uses a variable `i` to keep track of the current index in the array.
* **Method 2:** Modern `for...of` loop with index. This uses a variable `index` to keep track of the current index in the array, but it's not using the traditional indexing approach.

**Pros and Cons**

Here are some pros and cons of each method:

* **For loop with index:**
	+ Pros:
		- Faster execution speed (in this case, 40.28 EPS)
		- More predictable and controlled iteration process
	+ Cons:
		- Less concise code
		- Requires explicit indexing
* **For...of loop with index:**
	+ Pros:
		- Concise code syntax
		- Easy to read and write
	+ Cons:
		- Slower execution speed (in this case, 1.5 EPS)
		- May have performance implications in large datasets

**Other Considerations**

When deciding between these two methods, consider the following:

* **Array size:** If you're working with small arrays, the difference in execution speed might not be noticeable.
* **Iteration frequency:** If you're iterating over an array frequently, using a `for` loop with index might provide better performance.
* **Code readability:** If code conciseness is important, consider using a `for...of` loop with index.

**No Libraries Used**

There are no external libraries used in this test case. The tests are purely JavaScript-based.

**No Special JS Features or Syntax Used**

There are no special JavaScript features or syntax used in this test case.

**Alternatives**

If you're looking for alternative ways to iterate over an array, consider the following:

* **Map() function:** Use `map()` to create a new array with transformed values.
* **Filter() function:** Use `filter()` to create a new array with filtered values.
* **forEach() method:** Use `forEach()` to iterate over an array without modifying it.

Keep in mind that these alternatives might have different performance implications depending on your use case.

Related benchmarks:

for vs for in with index 2 (version: 0)

Comparing performance of: for vs for..of with index

Created: 3 years ago by: Guest

Jump to the latest result

for

for..of with index

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.1:latest, generated one month ago):