Benchmark: forEach vs for ... of

Script Preparation code:

function generateTestArray() {
  const result = [];
  for (let i = 0; i < 1000000; ++i) {
    result.push({
      a: i,
      b: i / 2,
      r: 0,
    });
  }
  return result;
}

Tests:

forEach
const a = generateTestArray(); a.forEach( b => b*2 );
for of
const a = generateTestArray(); for ( let b of a) { b=b*2; }

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

Latest run results:

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

User agent: Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/134.0.0.0 Mobile Safari/537.36

Browser/OS: Chrome Mobile 134 on Android

View result in a separate tab

Test name	Executions per second
forEach	5.8 Ops/sec
for of	5.6 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 and explain what is tested in the microbenchmark.

**Benchmark Purpose**

The benchmark compares the performance of two approaches: `forEach` and `for...of`. The test creates an array of 1,000,000 objects and then iterates over it using both methods. In each iteration, a specific operation is performed on each object (in this case, multiplying the `b` value by 2).

**Options Compared**

The two options compared are:

1. **`forEach`**: A traditional, callback-based loop that accepts a function as an argument.
2. **`for...of`**: A newer, more modern looping construct that iterates over arrays and other iterable objects.

**Pros and Cons of Each Approach**

* **`forEach`**:
	+ Pros: Well-established, widely supported, and easy to use.
	+ Cons: Can be slower than `for...of` due to the overhead of callback functions.
* **`for...of`**:
	+ Pros: More efficient, modern, and easier to read than `forEach`.
	+ Cons: May not work as expected with older browsers or non-array iterables.

**Library and Syntax**

None of the test cases use any external libraries. The syntax used is standard JavaScript (ES6+).

**Special JS Features or Syntax**

There are no special features or syntaxes mentioned in this benchmark.

**Other Alternatives**

In addition to `forEach` and `for...of`, other looping constructs that could be compared in a similar benchmark might include:

* `while` loops
* `do-while` loops
* `map()`, `filter()`, and `reduce()` methods (which are related to `forEach` but offer more functional programming features)

In terms of modern alternatives, the comparison between `forEach` and `for...of` is quite straightforward. However, if you were to expand this benchmark to compare other looping constructs or explore more advanced JavaScript features, the options would increase.

For example, if you wanted to compare the performance of different array methods like `map()`, `filter()`, and `reduce()` against traditional loops (like `forEach`), that could be an interesting exploration. Alternatively, comparing these constructs against more modern alternatives like WebAssembly or other JavaScript engines would provide a deeper insight into the nuances of JavaScript performance.

Related benchmarks:

forEach vs for ... of (version: 0)

Comparing performance of: forEach vs for of

Created: 2 years ago by: Guest

Jump to the latest result

forEach

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):