Benchmark: Arrays into Object, reduce vs for #4

Script Preparation code:

var ppl = []
for(var i=0; i<100000; i++) {
	ppl.push({ id: i, name: i+"" }) 
}

Tests:

reduce
var byId = ppl.reduce((stored, current) => ({ ...stored, [current.id]: current }), {});
for
var byId = {} for(var i=0;i<ppl.length;i++) { byId[ppl[i].id] = ppl[i] }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
reduce
for

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.67 Safari/537.36

Browser/OS: Chrome 87 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
reduce	0.1 Ops/sec
for	35.6 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the benchmark and explain what's being tested.

**Benchmark Overview**

The benchmark compares two approaches to create an object from an array of objects: using the `reduce()` method versus using a traditional `for` loop.

**Test Cases**

There are two test cases:

1. **"reduce"`**: This test case uses the `reduce()` method to create an object where each key is a unique ID and the corresponding value is the original object.
```javascript
var byId = ppl.reduce((stored, current) => ({ ...stored, [current.id]: current }), {});
```
This approach is often considered more concise and expressive than the traditional `for` loop method.

2. **"for"`**: This test case uses a traditional `for` loop to create an object where each key is a unique ID and the corresponding value is the original object.
```javascript
var byId = {};
for (var i = 0; i < ppl.length; i++) {
  byId[ppl[i].id] = ppl[i];
}
```
This approach can be more verbose, but it's often considered easier to understand for developers who are familiar with traditional loop constructs.

**Comparison**

The benchmark measures the performance of both approaches on a large array of objects (100,000 elements).

**Pros and Cons**

**`reduce()` method:**

Pros:

* Concise and expressive syntax
* Can be more readable and maintainable

Cons:

* May have slower performance due to the overhead of creating a new object for each iteration

**Traditional `for` loop:**

Pros:

* Often faster performance due to the predictability of the loop iterations
* Easier to debug and understand for developers familiar with traditional loop constructs

Cons:

* More verbose syntax, which can make it harder to read and maintain

**Other Considerations**

* The benchmark uses a relatively small array size (100,000 elements) compared to some real-world datasets. This may affect the performance differences between the two approaches.
* The `reduce()` method is often used in conjunction with other methods, such as `Object.keys()` or `Array.prototype.map()`, which can impact its performance.
* The traditional `for` loop approach may have additional overhead due to the need to manually manage the object's properties.

**Library and Special JS Features**

There are no libraries used in this benchmark. However, some JavaScript engines (e.g., V8) provide optimized implementations of the `reduce()` method that can improve performance.

No special JavaScript features or syntax are mentioned in this benchmark.

**Alternatives**

Other approaches to create an object from an array of objects include:

* Using `Object.assign()` and `Array.prototype.map()`
* Using a library like Lodash (`_.mapKeys()`)

Related benchmarks:

Arrays into Object, reduce vs for #4 (version: 0)

https://www.youtube.com/watch?v=5nzBDkH9lWI

Comparing performance of: reduce vs for

Created: 4 years ago by: Guest

Jump to the latest result

reduce

for

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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