Benchmark: Array loop vs foreach vs map 10k

Script Preparation code:

   var arr = [];
    for (var i = 0; i < 10000; i++) {
      arr[i] = i;
    }
  
    function someFn(i) {
      return i * 3 * 8;
    }

Tests:

foreach
arr.forEach(function (item){ someFn(item); })
for
for (var i = 0, len = arr.length; i < len; i++) { someFn(arr[i]); }
map
arr.map(item => someFn(item))

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
foreach
for
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 JSON data to explain what is being tested and compare different approaches.

**Benchmark Description**

The benchmark is designed to measure the performance of three JavaScript loop constructs: `foreach`, `for`, and `map`. The script preparation code creates an array `arr` with 10,000 elements, each initialized with a unique value. The function `someFn(i)` takes an integer `i` as input and returns its product multiplied by 3 and 8.

**Loop Constructs Compared**

The three loop constructs being compared are:

1. **Foreach**: This approach uses the `forEach()` method to iterate over the array, calling the callback function for each element.
2. **For**: This traditional loop construct iterates over the array using a `for` loop, accessing each element by its index.
3. **Map**: The `map()` method applies a transformation function to each element of the array, returning a new array with the transformed values.

**Pros and Cons**

Here's a brief summary of the pros and cons of each approach:

* **Foreach**:
	+ Pros: concise and easy to read, eliminates index management.
	+ Cons: can be less performant due to function call overhead, may suffer from cache thrashing (more on this later).
* **For**:
	+ Pros: direct access to array elements, minimal overhead.
	+ Cons: requires manual indexing, can lead to more complex code.
* **Map**:
	+ Pros: concise and expressive, avoids index management issues.
	+ Cons: creates a new array with transformed values, may incur additional memory allocations.

Regarding cache thrashing, it occurs when the `forEach()` method iterates over the array and modifies its internal state (e.g., updating the length property), which can cause the browser's cache to become disorganized. This might lead to slower performance for certain workloads.

**Library Usage**

The benchmark uses the `someFn` function, which is a simple multiplication function. However, it does not define any external libraries or frameworks that would impact the benchmark results.

**Special JS Features**

There are no special JavaScript features or syntax used in this benchmark, such as async/await, Promises, or web workers.

**Alternative Approaches**

If you're interested in exploring alternative loop constructs or optimization techniques, consider the following:

* **Reduce**: The `reduce()` method is another array method that can be used for iteration. It's similar to `map()`, but returns a single value instead of an array.
* **While loops**: Traditional while loops are another option, which provide direct access to array elements and can be more efficient than the loop constructs compared in this benchmark.

**Additional Considerations**

When benchmarking JavaScript performance, it's essential to consider factors such as:

* Input size: The larger the input size, the more significant the performance differences between loop constructs.
* Browser version and platform: Different browsers may optimize or implement features differently, affecting benchmark results.
* Garbage collection: Frequent allocations and deallocations can impact performance.

When running this benchmark, be sure to consider these factors and ensure that your test environment accurately reflects real-world use cases.

Related benchmarks:

Array loop vs foreach vs map 10k (version: 0)

Comparing performance of: foreach vs for vs map

Created: 4 years ago by: Guest

Jump to the latest result

foreach

for

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):