Benchmark: Regular for vs forEach

Script Preparation code:

var a = (new Array(10000)).fill(0).map((x, i) => i)

Tests:

For loop
for (let i = 0; i < a.length; i++) { console.log(a[i]) }
forEach
a.forEach(console.log)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
For loop
forEach

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 6 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.99 Safari/537.36

Browser/OS: Chrome 67 on Mac OS X 10.13.6

View result in a separate tab

Test name	Executions per second
For loop	4.2 Ops/sec
forEach	4.9 Ops/sec

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

LLMs can make mistakes. Check important info.

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

**Benchmark Overview**

The provided JSON represents two individual test cases: "For loop" and "forEach". Both tests aim to measure the performance of JavaScript loops on a specific dataset.

**Script Preparation Code**

The script preparation code is identical for both test cases:
```javascript
var a = (new Array(10000)).fill(0).map((x, i) => i);
```
This line creates an array `a` with 10,000 elements and assigns each element its index using the `map()` function.

**Html Preparation Code**

Neither of the test cases has an HTML preparation code, which means that only JavaScript code is being executed. This simplifies the benchmarking process by eliminating any overhead from HTML parsing or rendering.

**Test Cases**

**For loop**
```javascript
for (let i = 0; i < a.length; i++) {
  console.log(a[i]);
}
```
This test case uses a traditional `for` loop to iterate over the array `a` and logs each element to the console using `console.log()`.

**forEach**
```javascript
a.forEach(console.log);
```
This test case uses the `forEach()` method, which is a built-in JavaScript function that executes a callback function for each element in an array. In this case, the callback function simply logs the element to the console using `console.log()`.

**Library**

Neither of the test cases uses any external libraries. The `forEach()` method is a native JavaScript function, and there are no dependencies on third-party libraries.

**Special JS Feature or Syntax**

There are no special JavaScript features or syntax used in either test case that would require explanation.

**Comparison**

The two test cases aim to compare the performance of traditional `for` loops versus the `forEach()` method. The goal is to determine which approach is faster for iterating over an array and logging each element to the console.

**Pros and Cons**

**For loop:**

Pros:

* Well-established and widely supported syntax
* Can be optimized using techniques like loop unrolling or caching
* Easy to understand and maintain

Cons:

* Can be slower than native `forEach()` method due to function call overhead
* Requires explicit bounds checking (`i < a.length`)

**ForEach:**

Pros:

* Native JavaScript implementation, no additional dependencies required
* Faster execution compared to traditional `for` loop due to reduced function call overhead
* More concise syntax

Cons:

* Less intuitive syntax for beginners or those not familiar with the method
* May require explicit handling of edge cases (e.g., empty arrays)

**Benchmark Results**

The provided benchmark results show that Chrome 67 on a Mac OS X 10.13.6 device executed the `forEach()` test case approximately 1.21x faster than the traditional `for` loop test case.

**Other Alternatives**

For iterating over arrays and logging elements, other alternatives include:

* Using `Array.prototype.forEach.call()`, which is similar to the `forEach()` method but uses a more explicit callback function syntax.
* Utilizing libraries like Lodash or Underscore.js, which provide additional iteration utilities (e.g., `_.each()`).
* Leveraging modern JavaScript features like `for...of` loops or async/await for I/O-bound operations.

Keep in mind that the choice of iteration method ultimately depends on personal preference, project requirements, and performance considerations.

Related benchmarks:

Regular for vs forEach (version: 0)

Comparing performance of: For loop vs forEach

Created: 6 years ago by: Guest

Jump to the latest result

For loop

forEach

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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