Benchmark: Array loop vs foreach vs map with asssignment

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 (var i = 0, len = arr.length; i < len; i++) { someFn(arr[i]); }
map
let result1 = 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

Latest run results:

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

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**Benchmark Overview**

The provided benchmark measures the performance of three different JavaScript loop constructs: `forEach`, `for`, and `map` with assignment, when used to iterate over an array and perform a simple calculation on each element.

**Loop Constructs Comparison**

### 1. `forEach`

`forEach` is a method that calls a provided function once for each element in an array, without returning any value. In this benchmark, the `forEach` loop iterates over the `arr` array and calls the `someFn` function on each element.

Pros:

* Easy to read and understand
* Does not require manual index management

Cons:

* Can be less efficient than other methods due to its nature of iterating over the entire array in each iteration, resulting in more overhead from the JavaScript engine.
* May have additional overhead from the `for...of` loop that is used internally to iterate over the array.

### 2. `for`

The `for` loop uses a manual index to iterate over the elements of an array. In this benchmark, the `for` loop iterates over the `arr` array using a traditional `for` loop, where the variable `i` is incremented in each iteration.

Pros:

* Can be more efficient than `forEach` because it allows for manual control over the loop and avoids some overhead from the JavaScript engine.
* Allows for more flexibility in controlling the loop iterations

Cons:

* Requires manual index management, which can lead to errors if not done correctly
* Less readable than `forEach`

### 3. `map` with assignment

The `map` method returns a new array by applying a provided function to each element of an array. In this benchmark, the `map` loop iterates over the `arr` array and calls the `someFn` function on each element, assigning the result back to the original array.

Pros:

* Can be more efficient than `forEach` because it allows for caching of intermediate results
* Returns a new array with the transformed elements

Cons:

* May have additional overhead due to the creation of a new array
* Less readable than `forEach`

**Library Used: None**

There are no libraries used in this benchmark.

**Special JavaScript Features/Syntax: None**

There are no special JavaScript features or syntax used in this benchmark. The code is written in standard ECMAScript 2015 (ES6) syntax.

**Other Alternatives**

Other loop constructs that could be used to iterate over an array and perform a calculation on each element include:

* `while` loops
* `do...while` loops
* `for-in` loops (not recommended for iterating over arrays)
* Arrow functions (`=>`) with the `map` method

However, in this specific benchmark, only three loop constructs are compared: `forEach`, `for`, and `map`.

Related benchmarks:

Array loop vs foreach vs map with asssignment (version: 0)

Comparing performance of: foreach vs for vs map

Created: 6 years ago by: Guest

Jump to the latest result

foreach

for

map

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):