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:

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Autogenerated LLM Summary (model gemma2:9b, generated one year ago):

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This benchmark compares two different approaches to iterating over an array in JavaScript:

**Option 1:  `for` loop with index**

* **Benchmark Definition:** `const length = arr.length; for (let i = 0; i < length; i++) { arr[i] = arr[i] * 2; }`
* This classic approach uses a traditional `for` loop and explicitly tracks the index (`i`) of each element in the array.

**Option 2: `for...of` loop with index**

* **Benchmark Definition:** `let index = -1; for (let i of arr) { index++; i = i * 2; }`
* This method utilizes the more modern `for...of` loop, which iterates directly over each element in the array without requiring an explicit index.  We still add a variable `index` to mimic the traditional approach's behavior.

**Pros and Cons:**

* **`for` Loop:**
    * **Pros:** Well-established, widely understood syntax. Can be more performant for operations that heavily rely on indexed access.
    * **Cons:** More verbose, requires explicit index management. 
* **`for...of` Loop:**
    * **Pros:** Concise and cleaner syntax.  Easier to read and understand for iterating over elements.
    * **Cons:**  Can be slightly less performant than `for` loops in scenarios where indexed access is frequent.

**Other Considerations:**

* **Array Length:** The benchmark uses a relatively large array (100,000 elements). This is to make any performance differences more noticeable.

* **Task:** Both approaches perform the same operation: doubling each element's value. This is a simple operation that doesn't heavily rely on specific array features.

**Alternatives:**
* **`Array.forEach()`:** A higher-order function that iterates over an array and executes a provided callback function for each element.

Let me know if you have any more questions or want to explore other benchmark examples!

Related benchmarks:

for vs for in with index 2 (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 gemma2:9b, generated one year ago):