Benchmark: forEach vs reduce

Script Preparation code:

var a = Array.from({length:100},()=>Math.random());
var b = [];

Tests:

forEach
a.forEach(e=>{if (e>0.5) b.push(e)});
reduce
b = a.reduce((a,c)=>c>0.5?a.concat(c):a,[])

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: 6 years ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/65.0.3325.181 Safari/537.36

Browser/OS: Chrome 65 on Linux

View result in a separate tab

Test name	Executions per second
forEach	154726.1 Ops/sec
reduce	61315.0 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 JavaScript microbenchmark on MeasureThat.net and analyze what's being tested.

**What is being tested?**

The benchmark tests two approaches to iterate over an array:

1. `forEach` loop
2. `reduce` method

Both approaches are used to push elements greater than 0.5 into a new array (`b`) created from a random array of 100 numbers generated using `Array.from()` and `Math.random()`. The goal is to measure the performance difference between these two common iteration methods.

**Options compared**

In this case, there's only one option being tested for each approach:

* `forEach` loop with a callback function (`e => { if (e > 0.5) b.push(e); }`)
* `reduce` method with an initial value of an empty array (`[]`) and a callback function (`(a, c) => c > 0.5 ? a.concat(c) : a`)

**Pros and cons**

1. **forEach loop**: This approach is straightforward and easy to understand. However, it can be slower than other methods because the callback function needs to perform an additional comparison and push operation for each element.
2. **reduce method**: This approach is more concise and optimized for performance. The reduce method iterates over the array once, allowing the callback function to focus on a single element at a time, reducing overhead. However, it may be less intuitive for developers without prior experience with this method.

**Library usage**

There is no explicit library used in this benchmark, but `Array.from()` and `Math.random()` are built-in JavaScript functions.

**Special JS features or syntax**

None mentioned in the provided code snippets.

Now, let's consider alternative approaches that could be tested:

* Using a `for` loop instead of `forEach`
* Using `Array.prototype.filter()` to create the new array
* Using a library like Lodash or Underscore.js for iteration and filtering
* Testing the performance with different data sizes (e.g., 1000 elements)

Related benchmarks:

forEach vs reduce (version: 0)

Comparing performance of: forEach vs reduce

Created: 6 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):