Benchmark: forEach vs reduce vs for - fill object with object

Script Preparation code:

var arr = [];
for (var i = 0; i < 50000; i++) {
  arr.push(i);
}

Tests:

forEach
var objForEach = {}; arr.forEach(item => { objForEach[item] = { exists: true }; });
reduce
var objReduce = arr.reduce((acc, item) => { acc[item] = { exists: true }; return acc; }, {});
for
var objFor = {}; for (var j = 0; j < arr.length; j++) { var item = arr[j]; objFor[item] = { exists: true }; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
forEach
reduce
for

Fastest: N/A

Slowest: N/A

Autogenerated LLM Sumamry (model llama3.1:latest, generated 4 days ago):

LLMs can make mistakes. Check important info.

Let's dive into the benchmark.

**What is being tested?**

The benchmark is testing three different ways to fill an object (`objForEach`, `objReduce`, and `objFor`) with data from an array (`arr`) of 50,000 items. The goal is to compare the performance (speed) of these three approaches: using `forEach`, `reduce`, and a traditional `for` loop.

**What options are compared?**

The benchmark compares three options:

1. **ForEach**: Using the `forEach` method on the array to iterate over its elements and add them to an object.
2. **Reduce**: Using the `reduce` method on the array to accumulate an object with the desired data.
3. **For Loop**: Using a traditional `for` loop to iterate over the array's elements and add them to an object.

**Pros/Cons of each approach:**

*   **ForEach**:
    *   Pros: Easy to read and write, concise code.
    *   Cons: May not be as efficient as other methods for large datasets.
*   **Reduce**:
    *   Pros: Efficient and can handle large datasets well. Also, it's a functional programming approach which some developers prefer.
    *   Cons: Can be less readable than `forEach` or `for` loops for simple use cases.
*   **For Loop**:
    *   Pros: Can be more efficient than `forEach` for very large datasets and is easy to read. It's also a traditional looping approach which many developers are familiar with.
    *   Cons: May not be as concise as `forEach` or `reduce`, and can lead to more boilerplate code.

**Other considerations:**

*   **Library usage**: None in this benchmark, so no library explanation is needed.
*   **Special JS feature or syntax**: The use of arrow functions (`=>`) in the `forEach` test case. This is a modern JavaScript feature (introduced with ES6) that allows for concise function definitions.

**Other alternatives:**

You could also compare other methods such as using a `map` function, or even using a library like Lodash's `each` method if you want to see how they perform in comparison.

Latest run results:

Run details: (Test run date: 4 years ago)

User agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/81.0.4044.122 Safari/537.36

Browser/OS: Chrome 81 on Windows 7

View result in a separate tab

Test name	Executions per second
forEach	86.2 Ops/sec
reduce	106.1 Ops/sec
for	17.0 Ops/sec

Related benchmarks:

forEach vs reduce vs for - fill object with object (version: 0)

Comparing performance of: forEach vs reduce vs for

Created: 4 years ago by: Guest

Jump to the latest result

forEach

reduce

for

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Sumamry (model llama3.1:latest, generated 4 days ago):