Benchmark: for vs for in with index

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) { 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:

No previous run results

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

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Let's break down the provided benchmark JSON and explain what's being tested, compared, and considered.

**Benchmark Overview**

The benchmark measures the performance difference between three approaches:

1. **Traditional `for` loop**: Using an index variable to iterate over an array.
2. **`for...of` loop with index access**: Using the `of` clause to iterate over an array, and accessing each element's index directly.
3. **Using array length**: Iterating over an array using its length property.

**Test Cases**

The individual test cases are:

1. **Traditional `for` loop**: The script preparation code creates an empty array `arr` and then iterates over it 100,000 times using a traditional `for` loop, multiplying each element by 2.
2. **`for...of` loop with index access**: This test case uses the `of` clause to iterate over the same array `arr`. The script preparation code creates an empty array and then iterates over it 100,000 times using a `for...of` loop, accessing each element's index directly (although this is not necessary, as the variable is not used).
3. **Using array length**: This test case uses the `length` property of the array to iterate over it 100,000 times.

**Options Compared**

The benchmark compares three approaches:

* Traditional `for` loop
* `for...of` loop with index access (not necessary in this case)
* Using array length

Each approach has its pros and cons:

* **Traditional `for` loop**: This is a simple and straightforward approach. However, it may not be as efficient for large datasets, as it requires manual incrementation of the index variable.
* **`for...of` loop with index access**: While this approach uses the `of` clause to iterate over the array, accessing each element's index directly is unnecessary in this case. This approach may incur additional overhead due to the unnecessary operations.
* **Using array length**: This approach can be more efficient than traditional loops, as it eliminates the need for manual incrementation of an index variable. However, it may not be suitable for all scenarios, such as when working with dynamic data or requiring iteration over a specific range.

**Library and Special JS Features**

No libraries are used in this benchmark. No special JavaScript features are mentioned.

**Other Considerations**

The benchmark considers factors such as:

* **Browser and device platform**: The results are reported for different browsers (Chrome 90) and devices (Desktop).
* **Operating system**: The results are reported for Windows.
* **Execution speed**: The benchmark measures the execution speed of each approach, reporting the number of executions per second.

**Alternatives**

If you're interested in exploring alternative approaches or optimizing performance:

* Consider using iterative algorithms or loops that avoid manual incrementation of index variables.
* Look into modern JavaScript features like `for-await-of` or `map()`/`forEach()` for more efficient array iteration.
* Experiment with different data structures, such as sparse arrays or typed arrays, to optimize performance.

Keep in mind that the choice of approach depends on your specific use case and requirements. This benchmark provides a starting point for exploration and comparison, but you may need to experiment further to find the most suitable solution for your needs.

Related benchmarks:

for vs for in with index (version: 0)

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

Created: 5 years ago by: Guest

Jump to the latest result

for

for..of with index

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):