Benchmark: for of vs for vs foreach

Script Preparation code:

var arr = [1,2,3,4,5,6,7,8,9,0];

Tests:

Foreach
let result1 = ""; arr.forEach(item => result1 += item);
For
let result2 = ""; for (let i = 0; i < arr.length; i++) { result2 += arr[i]; }
For of
let result3 = ""; for (let item of arr) { result3 += item; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Foreach
For
For of

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/145.0.0.0 Safari/537.36

Browser/OS: Chrome 145 on Linux

View result in a separate tab

Test name	Executions per second
Foreach	10653653.0 Ops/sec
For	13057939.0 Ops/sec
For of	14003485.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided JSON data and explain what each part represents.

**Benchmark Definition**

The `Benchmark Definition` section defines the JavaScript microbenchmark that will be executed. In this case, there are three different approaches to concatenate an array of numbers:

1. **Foreach**: Uses the `forEach()` method to iterate over the array.
2. **For**: Uses a traditional `for` loop to iterate over the array.
3. **For of**: Uses the `of` syntax with the `for...of` loop to iterate over the array.

**Test Cases**

Each test case represents a specific execution of one of the three approaches. The code for each test case is provided in the `Benchmark Definition`.

* **Foreach**: The `forEach()` method is used to iterate over the array, and the result is concatenated using the `+=` operator.
* **For**: A traditional `for` loop is used to iterate over the array, and the result is concatenated using the `+=` operator.
* **For of**: The `of` syntax is used with the `for...of` loop to iterate over the array, and the result is concatenated using the `+=` operator.

**Library**

In the provided code snippets, the `forEach()` method is a part of the ECMAScript standard library, which means it is built-in to JavaScript. It provides a way to execute a function once for each element in an array or an object that implements the Iterable protocol.

**Special JS Feature/Syntax**

The `for...of` loop and the `of` syntax are part of the ECMAScript 2015 (ES6) specification. The `for...of` loop is designed to iterate over iterable objects, such as arrays, sets, maps, and more. The `of` syntax allows you to specify the iterable object that you want to iterate over.

**Pros and Cons**

Here are some pros and cons of each approach:

* **Foreach**: Pros: concise and easy to read; Cons: may be slower due to function call overhead.
* **For**: Pros: control over iteration order; Cons: less readable than `forEach()` or `for...of`.
* **For of**: Pros: concise and expressive; Cons: may be slower due to type checking.

**Other Alternatives**

If you wanted to use different approaches for concatenating an array, you could consider the following alternatives:

* Using a loop with an index variable (e.g., `let result = ''; for (let i = 0; i < arr.length; i++) { result += arr[i]; }`)
* Using a library like Lodash's `_.concat()` function
* Using a streaming approach, where you process the array in chunks

Keep in mind that these alternatives may have different performance characteristics and trade-offs.

I hope this explanation helps! Let me know if you have any further questions.

Related benchmarks:

for of vs for vs foreach (version: 9)

Comparing performance of: Foreach vs For vs For of

Created: 5 years ago by: Registered User

Jump to the latest result

Foreach

For

For of

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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