Benchmark: forEach vs reduce to make Object

Script Preparation code:

var arr = [];
for (var i = 0; i < 12345; i++) {
  arr[i] = i;
}

Tests:

forEach
const value = {} arr.forEach(item => {if(item % 2 === 0) {value[item] = true}}); return value
reduce
sumReduce = arr.reduce((value, item) => { if(item % 2 === 0) {value[item] = true}; return value }, {}); return arr

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
forEach
reduce

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/90.0.4430.93 Safari/537.36

Browser/OS: Chrome 90 on Linux

View result in a separate tab

Test name	Executions per second
forEach	1236.2 Ops/sec
reduce	1216.7 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the explanation of the provided benchmark.

**Benchmark Definition**

The benchmark is designed to compare the performance of two JavaScript array methods: `forEach` and `reduce`. Specifically, it tests how these methods perform when used to iterate over an array and create a new object that marks even numbers as true.

**Options Compared**

Two approaches are compared:

1. **forEach**: This method iterates over each element in the array using a callback function. In this benchmark, the callback checks if the current item is even and adds it to the `value` object.
2. **reduce**: This method applies a reducer function to each element in the array, accumulating a value that's returned as the result of the operation.

**Pros and Cons**

* **forEach**:
	+ Pros: Easy to understand and implement, straightforward approach for iterating over an array.
	+ Cons: Can be slower than `reduce` because it creates multiple intermediate objects (one for each item in the array), whereas `reduce` accumulates the values in a single object.
* **reduce**:
	+ Pros: More memory-efficient than `forEach`, as it accumulates values in a single object. It's also more concise and expressive, as it returns the final result directly.
	+ Cons: Requires more expertise to implement correctly, especially for complex reduction functions.

**Library Used**

None of the benchmark tests use external libraries.

**Special JS Features or Syntax**

There are no special JavaScript features or syntax used in this benchmark.

**Other Considerations**

When writing performance benchmarks like this one, consider the following:

* Use a representative dataset (in this case, an array of 12345 elements).
* Keep the test cases simple and focused on a specific use case.
* Run multiple iterations to get reliable results.
* Measure execution times accurately using a suitable timer.

**Alternatives**

Other alternatives for iterating over arrays in JavaScript include:

1. **For...of loop**: A more modern and concise approach, which is supported by most browsers.
2. **Array.prototype.forEach.call()**: Similar to the `forEach` method, but provides more flexibility with array-like objects.
3. **while` loops**: A low-level approach that allows for fine-grained control over iteration.

Keep in mind that these alternatives might have different performance characteristics compared to the methods tested in this benchmark.

Related benchmarks:

forEach vs reduce to make Object (version: 0)

Comparing performance of: forEach vs reduce

Created: 3 years ago by: Guest

Jump to the latest result

forEach

reduce

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):