Benchmark: for vs forEach - MeasureThat.net

Script Preparation code:

var testArray = [];

for (var i = 1; i <= 100; i++) {
   testArray.push(i);
}

Tests:

for loop
for(var i = 0, length = testArray.length; i < length; i += 1) { testArray[i] += 1; for(var j = 0, length = testArray.length; j < length; j += 1) { testArray[i] += 1; } }
forEach
testArray.forEach((item) => { item += 1; });
Map
testArray.map((item) => { item += 1; });

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for loop
forEach
Map

Fastest: N/A

Slowest: N/A

Latest run results:

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmarking JSON and explain what is being tested.

**Benchmark Overview**

The benchmark measures the performance of three different approaches to increment each element in an array:

1. **For Loop**: A traditional `for` loop that iterates over the array using a counter variable.
2. **ForEach**: The `forEach` method, which iterates over the array and executes a callback function for each element.
3. **Map**: The `map()` method, which returns a new array with the results of applying a provided function to each element in the original array.

**Comparison**

The benchmark compares these three approaches because they have different performance characteristics:

* For Loop: This approach iterates over the array using a counter variable, which can lead to slower performance due to the overhead of incrementing the counter and accessing array elements.
* For Each/Map: These approaches use built-in JavaScript methods that are optimized for performance. `forEach` executes the callback function once per element, while `map()` returns a new array with the transformed elements in a single pass.

**Pros and Cons**

Here's a brief summary of each approach:

* **For Loop**: Pros:
	+ Simple and easy to understand
	+ Can be faster for small arrays or specific use cases
Cons:
	+ Slow due to counter incrementation and array access overhead
* **ForEach**: Pros:
	+ Optimized performance for iterating over arrays
	+ Easy to read and maintain code
Cons:
	+ Limited flexibility compared to `map()`
* **Map**: Pros:
	+ Fast performance with a single pass through the array
	+ Returns a new array, which can be useful for caching or transformations
Cons:
	+ Can be less readable than `forEach` due to the use of `map()` and arrow functions

**Library**

In this benchmark, there is no explicit library used. However, it's worth noting that some browsers might include internal optimizations or polyfills for these methods.

**Special JS Features/Syntax**

This benchmark uses:

* **Arrow Functions**: The callback functions in `forEach` and `map()` use arrow functions (`(item) => { ... }`). While not a special feature per se, arrow functions can be an important aspect of modern JavaScript syntax.
* **Template Literals**: Although not explicitly used in the provided code snippets, template literals (e.g., `var testArray = [];\r\n\r\nfor (var i = 1; i <= 100; i++) {\r\n   testArray.push(i);\r\n};`) are used in the script preparation code.

**Other Alternatives**

If you're looking for alternative approaches to incrementing each element in an array, consider:

* **Using a `reduce()` method**: Instead of `forEach` or `map()`, you can use the `reduce()` method with a callback function to achieve similar results.
* **Using a simple loop with indexing**: You could write a custom loop using array indexing (`arr[i] += 1;`) for each element, but this would likely be slower than the built-in methods.

Keep in mind that the choice of approach depends on your specific use case and performance requirements.

Related benchmarks:

for vs forEach (version: 0)

Comparing performance of: for loop vs forEach vs Map

Created: 8 years ago by: Guest

Jump to the latest result

for loop

forEach

Map

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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