Benchmark: forEach vs for-of

Tests:

forEach
const array = [{ id: 1, name: 'Bob' }, { id: 2, name: 'Sarah' }, { id: 2, name: 'Amy' }, { id: 2, name: 'Joe' }]; try { array.forEach(function(item, idx) { if (idx === 2) { throw new Error(); } }); } catch (ignore) { }
for-of
const array = [{ id: 1, name: 'Bob' }, { id: 2, name: 'Sarah' }, { id: 2, name: 'Amy' }, { id: 2, name: 'Joe' }]; let idx = 0; for (const item of array) { if (idx === 2) { break; } idx++; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
forEach
for-of

Fastest: N/A

Slowest: N/A

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

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Let's break down the provided benchmark and explain what's being tested.

**Benchmark Overview**

The benchmark compares two approaches to iterate over an array in JavaScript:

1. `forEach` loop
2. `for-of` loop (also known as "iterator-based for loop")

**Options Compared**

The `forEach` approach uses a traditional loop with the `Array.prototype.forEach()` method, which iterates over the array using an iterator.

The `for-of` approach uses a special type of loop that allows iterating directly over an array's elements without the need for indexing or iterator objects. This loop is optimized for modern JavaScript engines.

**Pros and Cons**

**forEach Approach:**

Pros:

* More readable code, as it explicitly iterates over each element in the array.
* Easier to understand for developers familiar with traditional loops.

Cons:

* Can be slower due to the overhead of creating an iterator object and iterating over it.

**for-of Approach:**

Pros:

* Faster execution speed, as modern JavaScript engines can optimize this type of loop more effectively.
* More concise code, making it easier to write and read.

Cons:

* Less readable for developers unfamiliar with this specific syntax.
* May require additional setup or context to understand the iteration logic.

**Library Used (if any)**

There is no library used in this benchmark. Both `forEach` and `for-of` are built-in JavaScript constructs.

**Special JS Feature/Syntax**

The `for-of` loop uses a special syntax, introduced in ECMAScript 2015 (ES6), which allows iterating directly over an array's elements without the need for indexing or iterator objects.

Here's a brief explanation of this syntax:

```javascript
for (const item of array) {
    // code here
}
```

This loop is designed to work with arrays, but it can also be used with other iterable values like sets and maps. The `const` keyword is used to declare the variable `item`, which takes on each element value in the iteration.

**Other Alternatives**

If you need to iterate over an array, there are additional alternatives:

1. **Traditional `for` loop**: Similar to the `forEach` approach, but uses a traditional index-based loop.
```javascript
for (let i = 0; i < array.length; i++) {
    // code here
}
```

2. **Array.prototype.map()`, Array.prototype.filter()**, or Array.prototype.reduce()**: While not exactly iteration over an array, these methods can be used to process arrays in a functional programming style.

In this benchmark, the `for-of` approach is shown to be faster than the traditional `forEach` loop, highlighting its potential for performance advantages in modern JavaScript engines.

Related benchmarks:

forEach vs for-of (version: 0)

Comparing performance of: forEach vs for-of

Created: 7 years ago by: Guest

Jump to the latest result

forEach

for-of

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):