Benchmark: for vs for..of vs forEach, arrow function

Script Preparation code:

var array = new Array(1000);

Tests:

for native
for (let i = array.length - 1; i >= 0; i--) { array[i]; }
for
for (let i = 0; i < array.length; i++) { array[i]; }
forEach
array.forEach((x) => x);
some
array.some((x) => false);
for .. of
for (let i of array) { array[i]; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for native
for
forEach
some
for .. of

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/15.1 Safari/605.1.15

Browser/OS: Safari 15 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
for native	30804.0 Ops/sec
for	15159.8 Ops/sec
forEach	42476.9 Ops/sec
some	1825823.6 Ops/sec
for .. of	16855.7 Ops/sec

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

LLMs can make mistakes. Check important info.

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

**Benchmark Overview**

The provided benchmark measures the performance of different JavaScript loops for accessing elements in an array:

*   `for` loop
*   `for..of` loop (introduced in ECMAScript 2015)
*   `forEach` method
*   `some` method

**Loop Options Compared**

Here's a brief description of each loop option and their characteristics:

1.  **For Loop (`for`)**
    *   This is the traditional way to iterate over an array in JavaScript.
    *   It uses an incrementing index variable (`i`) to access elements in the array.
    *   Pros:
        *   Well-established syntax
        *   Easy to understand and implement
    *   Cons:
        *   Can be slower due to the overhead of managing the index variable

2.  **For..Of Loop (`for .. of` or `for...of`)**
    *   Introduced in ECMAScript 2015, this loop provides a more modern and concise way to iterate over arrays.
    *   It uses the value of each array element directly without creating an incrementing index variable.
    *   Pros:
        *   More readable code
        *   Less prone to errors (no need to worry about index variable management)
        *   Improved performance due to fewer operations
    *   Cons:
        *   Newer syntax might take some time for developers to get accustomed to

3.  **forEach Method**
    *   This method applies a provided function to each element of an array.
    *   It's often used with arrays, but also works with other iterable objects (like maps).
    *   Pros:
        *   Easy to use and understand
        *   Provides a clear intent for the code (i.e., apply a function to each element)
    *   Cons:
        *   Not directly applicable to accessing elements in an array; it's more suited for operations on arrays.

4.  **Some Method**
    *   This method returns `true` if at least one element of an array passes the test implemented by its provided function.
    *   Like `forEach`, it's often used with arrays, but also works with other iterable objects (like maps).
    *   Pros:
        *   Easy to use and understand
        *   Provides a clear intent for the code (i.e., check if at least one element passes a test)
    *   Cons:
        *   Not directly applicable to accessing elements in an array; it's more suited for operations on arrays.

**Library Usage**

None of the provided loops make use of external libraries. They are all built-in JavaScript features designed to work with native data types like arrays.

**Special JS Features or Syntax (if any)**

There is no explicit usage of special JS features or syntax beyond ECMAScript 2015 (specifically, the `for..of` loop).

**Benchmark Considerations**

The benchmark aims to compare the performance of different loop options for accessing elements in an array. The results will help determine which approach provides the best execution speed.

**Other Alternatives**

If you're interested in exploring alternative loop options or considering specific optimizations for your use cases, here are some additional points:

*   **While Loops**: For loops can also be used with arrays (e.g., `while` statements).
*   **Array Iterators**: If you need more control over the iteration process or want to optimize for a specific type of data structure, consider using an array iterator.
*   **Generators**: Generators provide a way to iterate over large datasets without loading them into memory at once.

In terms of optimizations, keep in mind that:

*   **Avoid unnecessary function calls**: In some cases, creating temporary variables or calling unnecessary functions can lead to performance overhead.
*   **Minimize array resizing**: For arrays with many elements, resizing the array during iteration can be slower than using a fixed-size array.
*   **Prefer in-place operations**: When possible, prefer operations that modify data in-place rather than allocating new memory.

These optimizations might require additional effort to implement and are often dependent on specific use cases or requirements.

Related benchmarks:

for vs for..of vs forEach, arrow function (version: 0)

Comparing performance of: for native vs for vs forEach vs some vs for .. of

Created: 2 years ago by: Guest

Jump to the latest result

for native

for

forEach

some

for .. of

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):