Benchmark: map vs foreach - MeasureThat.net

Script Preparation code:

var array = new Array(100);

Tests:

forEach
array.forEach(function(i) { array[i]; });
map
array.map(function(i) { array[i]; });

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
forEach
map

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 10 months ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/137.0.0.0 Safari/537.36

Browser/OS: Chrome 137 on Windows

View result in a separate tab

Test name	Executions per second
forEach	10068235.0 Ops/sec
map	7250748.5 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's being tested.

**Benchmark Definition**

The benchmark is testing two JavaScript methods: `forEach` and `map`. Both methods are used to iterate over an array, but they differ in how they handle the iteration.

**Options Compared**

Two options are compared:

1. **`array.forEach(function(i) { array[i]; });`**: This method uses the `forEach` loop to iterate over the array. The callback function takes an argument (`i`) that represents the index of the current element, but it's not actually used in this case. Instead, the callback tries to access the element at the current index (`array[i]`) without checking if the index is valid (out of bounds). This can lead to a runtime error.
2. **`array.map(function(i) { array[i]; });`**: This method uses the `map` function to create a new array with transformed elements. The callback function also takes an argument (`i`) that represents the index of the current element, similar to `forEach`. However, unlike `forEach`, `map` creates a new array and does not modify the original array.

**Pros and Cons**

1. **`array.forEach(function(i) { array[i]; });`**
	* Pros: None (it's a bad idea)
	* Cons:
		+ Can lead to runtime errors if the index is out of bounds.
		+ Not suitable for creating new arrays or modifying existing ones.
2. **`array.map(function(i) { array[i]; });`**
	* Pros:
		+ Creates a new array, which can be useful in some cases.
		+ Allows for transformation of elements while iterating over the original array.
	* Cons:
		+ Can lead to performance issues if the resulting array is large and the transformation is expensive.

**Library Used**

In this benchmark, there is no specific library being used. The `forEach` and `map` methods are built-in JavaScript methods that work with arrays.

**Special JS Feature/Syntax**

There is a special syntax used in both test cases: `$\r\n$`. This is just newline characters (`\n`) embedded in the code, which is not relevant to the benchmark itself. It's likely included to make the code more readable or for some other reason unrelated to the comparison.

**Other Considerations**

When writing JavaScript code, it's essential to consider how different methods will interact with arrays and avoid common pitfalls like using indices without bounds checking.

Alternative approaches:

* **Using `for` loops**: Instead of `forEach` or `map`, you could use traditional `for` loops to iterate over the array.
* **Using `reduce()`**: If you need to transform an array, consider using the `reduce()` method instead, which can be more efficient than `map`.
* **Caching results**: In some cases, you might want to cache the result of a calculation or transformation to avoid repeated computations.

The provided benchmark highlights the importance of choosing the right method for your specific use case and considering potential pitfalls.

Related benchmarks:

map vs foreach (version: 0)

Comparing performance of: forEach vs map

Created: 4 years ago by: Guest

Jump to the latest result

forEach

map

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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