Benchmark: for of loop vs. .map

Script Preparation code:

// Create sample data
var array = [1,2,3,4,5,6,7,8,9,0];

var manipulateFn = num => {
	return num * 2 * 3;
}

Tests:

.map
var newArray = array.map( i => manipulateFn(i));
for loop
var newArray = []; for (const item of array) { newArray.push(manipulateFn(item)); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
.map
for loop

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 months ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; ) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/126.0.6478.61 Chrome/126.0.6478.61 Not/A)Brand/8 Safari/537.36

Browser/OS: Chrome 126 on Windows

View result in a separate tab

Test name	Executions per second
.map	8687036.0 Ops/sec
for loop	7652267.5 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated 4 months ago):

LLMs can make mistakes. Check important info.

The benchmark defined in the provided JSON compares two different approaches to transforming elements in an array using JavaScript: the `.map` method and the `for...of` loop. Both approaches aim to apply a manipulation function (`manipulateFn`) to each element of an array and produce a new array with the transformed results.

### Options Compared:

1. **`.map()` Method**
   - **Benchmark Definition**: `var newArray = array.map(i => manipulateFn(i));`
   - **Test Name**: `.map`

2. **`for...of` Loop**
   - **Benchmark Definition**: 
     ```javascript
     var newArray = [];
     for (const item of array) {
         newArray.push(manipulateFn(item));
     }
     ```
   - **Test Name**: `for loop`

### Pros and Cons:

#### `.map()` Method
- **Pros**:
  - **Concise and Expressive**: The `.map` method is a higher-order function, which means it takes a function as an argument and operates on the array in a more declarative way.
  - **Functional Programming Style**: Encourages immutability by returning a new array without modifying the original one.
  - **Readability**: Often easier to read for developers familiar with functional programming concepts.

- **Cons**:
  - **Performance Overhead**: In some cases, `.map()` may introduce overhead due to the function calls made for each element, potentially leading to slower performance for large datasets compared to a simple loop.
  - **Less Control**: It might not be as straightforward to implement more complex or conditional logic that doesn't fit the functional paradigm.

#### `for...of` Loop
- **Pros**:
  - **Performance**: In certain scenarios, a `for...of` loop can be faster because it provides more control over the iteration and does not incur the overhead of higher-order functions.
  - **Flexibility**: Allows for complex logic and condition handling inside the loop, making it easier to customize behavior for specific elements.

- **Cons**:
  - **Verbosity**: Requires more lines of code to achieve the same result as `.map`, which may lead to less readability, especially for straightforward transformations.
  - **Mutability**: May introduce mutability issues if not managed carefully, as the loop can modify the original array instead of just creating a new one.

### Other Considerations:
- **Performance Metrics**: The benchmark results show that when this test was run in Chrome, the `.map` method performed better with **18,702,624 executions per second**, compared to **13,725,970 executions per second** for the `for...of` loop. This highlights that, at least in this specific case and environment, the functional approach was faster.
- **Use Case**: The choice between these two options should depend on the specific requirements of the task at hand. If performance in a critical part of an application is paramount, it is worth testing both approaches. However, for readability and cleaner code, `.map()` is often favored in situations where performance is not an issue.

### Alternatives:
Apart from `.map()` and `for...of`, there are other alternatives for iterating over arrays in JavaScript:

- **Classic `for` Loop**: 
  ```javascript
  for (let i = 0; i < array.length; i++) {
      newArray.push(manipulateFn(array[i]));
  }
  ```
  This can sometimes outperform both `.map()` and `for...of` due to less overhead.

- **`forEach()` Method**: Similar to `.map()`, but primarily used for performing actions on each array element rather than transforming them.
  ```javascript
  array.forEach(item => newArray.push(manipulateFn(item)));
  ```
  This does not create a new array and could be less optimal if you also need the result.

### Conclusion:
In summary, the benchmark tests two widely-used array transformation techniques in JavaScript. Understanding the differences, pros, cons, and performance can help software engineers make informed decisions when writing transform operations on arrays. Whether to prioritize performance or code readability will often influence which approach is best suited to a particular situation.

Related benchmarks:

for of loop vs. .map (version: 1)

Comparing performance of: .map vs for loop

Created: 4 months ago by: Registered User

Jump to the latest result

.map

for loop

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated 4 months ago):