Benchmark: for vs forEach vs some vs for..of vs for..in

Script Preparation code:

var array = new Array(1000).fill(0);

Tests:

for
for (let i = 0, length = array.length; i < length; i++) { array[i] }
foreach
array.forEach(item => item);
some
array.some(item => item);
for..of
for (let item of array) { item }
for..in
for (let i in array) { array[i] }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for
foreach
some
for..of
for..in

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one month ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/134.0.0.0 Safari/537.36

Browser/OS: Chrome 134 on Linux

View result in a separate tab

Test name	Executions per second
for	965846.7 Ops/sec
foreach	3683488.8 Ops/sec
some	1826720.2 Ops/sec
for..of	3725722.5 Ops/sec
for..in	60997.2 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):

LLMs can make mistakes. Check important info.

The provided JSON represents a JavaScript benchmark that compares the performance of different loop constructs: `for`, `forEach`, `some`, and two variations of `for`: `for...of` and `for...in`. Let's break down each option:

**1. Traditional `for` loop**

```javascript
for (let i = 0, length = array.length; i < length; i++) {
    array[i];
}
```

This is the most straightforward way to iterate over an array in JavaScript. The `length` property of the array object returns the number of elements in the array.

Pros:

* Easy to understand and implement
* Works well with arrays, objects, and other iterable data structures

Cons:

* Can be slow for large datasets because it involves accessing the `length` property on each iteration, which can lead to unnecessary memory access.
* Does not provide any feedback about the number of elements processed or errors encountered.

**2. `forEach` loop**

```javascript
array.forEach(item => item);
```

The `forEach` method is a modern JavaScript construct that allows iterating over arrays and other iterable data structures without manual index management. It takes two arguments: an optional callback function, which is called for each element in the array, and a `this` context.

Pros:

* Efficiently uses the optimized Array.prototype.forEach implementation.
* Does not require manual memory management or access to the `length` property.
* Provides built-in feedback about the number of elements processed.

Cons:

* Requires JavaScript 5.0+ (released with ECMAScript 262, 3rd edition) for use in modern browsers and Node.js environments.
* Not available in older JavaScript engines or environments that do not support Array.prototype.forEach.

**3. `some` loop**

```javascript
array.some(item => item);
```

The `some` method is another array iteration method that checks if at least one element of the array satisfies a provided callback function. It returns `true` as soon as it finds an element for which the callback returns true.

Pros:

* Similar to `forEach`, but with an added layer of optimization, as it short-circuits as soon as it finds an element for which the callback returns true.
* Can be useful when you only need to check if at least one element in the array meets a certain condition.

Cons:

* May not be immediately clear what its purpose is compared to `forEach`, due to its specific use case.
* Still requires JavaScript 5.0+ (released with ECMAScript 262, 3rd edition) for use in modern browsers and Node.js environments.

**4. `for...of` loop**

```javascript
for (let item of array) {
    item;
}
```

The `for...of` loop is a newer JavaScript construct that allows iterating over arrays, objects, and other iterable data structures using an iterator context. It is similar to the traditional `for` loop but provides more flexibility in terms of variable declaration.

Pros:

* Easy to read and understand for developers familiar with iterators or object values.
* Does not require manual memory management or access to the `length` property.
* Can be used for both arrays and objects, as well as other data structures that support iteration.

Cons:

* Requires JavaScript 2015+ (released with ECMAScript 6, ES6) for use in modern browsers and Node.js environments.
* May have a slight performance overhead compared to traditional `for` or `forEach` loops due to the added complexity of iterator management.

**5. `for...in` loop**

```javascript
for (let i in array) {
    array[i];
}
```

The `for...in` loop is an older JavaScript construct that allows iterating over objects and arrays using property iteration. It iterates over all enumerable properties, including non-standard ones, as well as own and inherited properties.

Pros:

* Works for both arrays and objects, but note it also includes non-enumerable properties.
* Can be used in environments where newer iteration methods are not supported.

Cons:

* May include unexpected iterations or errors due to non-enumerable properties.
* Not the recommended choice due to its complexity and potential issues with modern array data structures.

Now that we have covered each option, let's consider other alternatives for loop constructs. Some examples of alternative loops or methods in JavaScript include:

1.  `Array.prototype.reduce()` - Iterates over an array from left-to-right and performs a cumulative operation on elements.
2.  `Array.prototype.map()` - Creates new arrays by applying a provided function to each element in the original array.
3.  `Set.prototype.forEach()` or `Map.prototype.forEach()` - Iterate over sets or maps using callback functions.

When choosing between different loop constructs, consider factors like performance requirements (e.g., loops with high overhead can be detrimental for large datasets), data structure compatibility, and personal coding style preferences.

In the context of MeasureThat.net's benchmarking tests, selecting the optimal loop construct is essential to achieve accurate measurements. Based on your provided data, it seems that `for...of` provides the best performance results in this case.

Related benchmarks:

for vs forEach vs some vs for..of vs for..in (version: 1)

Compare loop performance

Comparing performance of: for vs foreach vs some vs for..of vs for..in

Created: 4 years ago by: Registered User

Jump to the latest result

for

foreach

some

for..of

for..in

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):