Benchmark: Array for vs foreach vs map

Script Preparation code:

   var arr = [];
    for (var i = 0; i < 1000; i++) {
      arr[i] = i;
    }
  
    function someFn(i) {
      return i * 3 * 8;
    }

Tests:

foreach
arr.forEach(function (item){ someFn(item); })
for
for (let el of arr) { someFn(el); }
map
arr.map(item => someFn(item))

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
foreach
for
map

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 28 days ago):

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what's being tested, the different approaches compared, their pros and cons, and other considerations.

**Benchmark Definition**

The benchmark is designed to measure the performance of three different approaches for iterating over an array in JavaScript:

1. `foreach` (also known as `forEach loop`)
2. `for` loop
3. `map` method

**Script Preparation Code**

The script preparation code creates a JavaScript array with 1000 elements, each initialized with its index (`i`) multiplied by 3 and 8 using the `someFn` function.

```javascript
var arr = [];
for (var i = 0; i < 1000; i++) {
  arr[i] = i * 3 * 8;
}
function someFn(i) {
  return i * 3 * 8;
}
```

This code sets up the array and defines a simple function (`someFn`) that is used in each iteration.

**Html Preparation Code**

There is no HTML preparation code provided, which means that the benchmark only runs in a JavaScript environment (e.g., Node.js, browser).

**Individual Test Cases**

Each test case represents one of the three approaches being compared:

1. **`foreach`**: This test case uses the `forEach` loop to iterate over the array and apply the `someFn` function to each element.
```javascript
arr.forEach(function (item) {
  someFn(item);
});
```

2. **`for` loop**: This test case uses a traditional `for` loop to iterate over the array and apply the `someFn` function to each element.
```javascript
for (let el of arr) {
  someFn(el);
}
```

3. **`map` method**: This test case uses the `map` method to create a new array with the results of applying the `someFn` function to each element in the original array.
```javascript
arr.map(item => someFn(item));
```

**Latest Benchmark Result**

The latest benchmark result shows the performance data for each test case:

| Test Case | Browser | Device Platform | Operating System | Executions Per Second |
| --- | --- | --- | --- | --- |
| `foreach` | Chrome 72 | Desktop | Mac OS X 10.13.6 | 16128.521484375 |
| `for` loop | Chrome 72 | Desktop | Mac OS X 10.13.6 | 16649.447265625 |
| `map` method | Chrome 72 | Desktop | Mac OS X 10.13.6 | 15342.8857421875 |

**Pros and Cons**

* **`foreach`**: This approach can be slower than the others because it uses a loop with an iterator, which can introduce overhead due to the creation of a closure.
* **`for` loop**: This approach is generally faster than `foreach` because it avoids creating a closure and uses a simpler iteration mechanism. However, it can still be slower than the `map` method for large datasets.
* **`map` method**: This approach creates a new array with the results of applying the function to each element, which can be slower due to memory allocation and copying. However, it also avoids creating a closure and can be faster than `foreach` for large datasets.

**Other Considerations**

* The benchmark does not account for the size of the input data or other factors that might affect performance.
* The `map` method assumes that the input array is sparse (i.e., most elements are null or undefined), which may not always be the case.
* The `foreach` loop uses a traditional iterator, which can lead to slower performance than modern JavaScript features like iterators and generators.

**Alternatives**

If you're looking for alternative approaches, consider the following:

* Use iterators or generators instead of traditional loops to avoid creating closures.
* Use the `reduce` method instead of `map` if you need to accumulate results in an array.
* Consider using a library like Lodash or Ramda that provides optimized implementations of common array operations.

Latest run results:

Run details: (Test run date: 5 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/72.0.3626.121 Safari/537.36

Browser/OS: Chrome 72 on Mac OS X 10.13.6

View result in a separate tab

Test name	Executions per second
foreach	16128.5 Ops/sec
for	16649.4 Ops/sec
map	15342.9 Ops/sec

Related benchmarks:

Array for vs foreach vs map (version: 0)

Comparing performance of: foreach vs for vs map

Created: 5 years ago by: Guest

Jump to the latest result

foreach

for

map

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 28 days ago):