Benchmark: Object.fromEntries vs reduce vs Map with small objects

Script Preparation code:

var data = { ...Array.from(Array(5).keys()) };

Tests:

Object.fromEntries
Object.fromEntries(Object.entries(data).map((key, value) => [key, value]));
Reduce (reuse object)
Object.entries(data).reduce((acc, [k, v]) => { acc[k] = v.toString(); return acc; }, {});
Reduce (creating temporary objects)
Object.entries(data).reduce((acc, [k, v]) => ({ ...acc, [k]: v.toString() }), {});
Map
Object.entries(data).reduce((acc, [k, v]) => { acc.set(k, v.toString()) return acc; }, new Map());

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Object.fromEntries
Reduce (reuse object)
Reduce (creating temporary objects)
Map

Fastest: N/A

Slowest: N/A

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 is being tested.

**Benchmark Overview**

The benchmark compares four different approaches to create an object from a list of key-value pairs:

1. `Object.fromEntries`
2. `Array.prototype.reduce` with reuse of the accumulator object
3. `Array.prototype.reduce` with creation of temporary objects
4. `Map`

The test case uses small objects, and the benchmark aims to determine which approach is the fastest.

**Options Compared**

Here's a brief overview of each option:

1. **Object.fromEntries**: This method was introduced in ECMAScript 2015 (ES6). It creates an object from an array of key-value pairs.
2. **Reduce (reuse object)**: In this approach, the accumulator object is reused throughout the reduction process. The `reduce` method is called with an initial value of `{}`, and each iteration modifies this object by adding new properties.
3. **Reduce (creating temporary objects)**: Similar to the previous approach, but a new object is created in each iteration to store the accumulated values.
4. **Map**: A `Map` is used as the accumulator object. This approach uses the `Map`'s `set` method to add key-value pairs.

**Pros and Cons**

Here's a brief analysis of each option:

1. **Object.fromEntries**:
	* Pros: Efficient, concise, and easy to read.
	* Cons: May not work as expected if the input array has duplicate keys (although this is mitigated by using `Object.fromEntries` with a `Map`-like object as its second argument).
2. **Reduce (reuse object)**:
	* Pros: Reuses the accumulator object, reducing memory allocation and deallocation overhead.
	* Cons: May lead to slower performance due to the reuse of an object that grows in size on each iteration.
3. **Reduce (creating temporary objects)**:
	* Pros: Creates a new object on each iteration, which can be faster than reusing an existing object.
	* Cons: Leads to more memory allocations and deallocations, which can slow down performance.
4. **Map**:
	* Pros: Efficient use of `Map`'s built-in features, such as fast lookups and insertions.
	* Cons: May have a higher overhead due to the creation of an additional object.

**Special JS Feature/Syntax**

None mentioned in this benchmark.

**Library Usage**

The `Array.prototype.reduce` method is used extensively throughout the benchmark. The `Map` constructor is also used, but not as part of a library or framework.

**Other Alternatives**

Some alternative approaches to creating objects from key-value pairs include:

1. **Using `Object.assign()`**: This method can be used to create an object by merging multiple objects together.
2. **Using a `for...of` loop and string interpolation**: This approach involves using a `for...of` loop to iterate over the key-value pairs and creating a new object using string interpolation.

These alternatives are not explored in this benchmark, but they may be worth considering depending on specific use cases.

I hope this explanation helps!

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/110.0.0.0 Safari/537.36

Browser/OS: Chrome 110 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Object.fromEntries	572082.9 Ops/sec
Reduce (reuse object)	2785124.8 Ops/sec
Reduce (creating temporary objects)	1702197.0 Ops/sec
Map	2031321.8 Ops/sec

Related benchmarks:

Object.fromEntries vs reduce vs Map with small objects (version: 0)

Test with small objects

Comparing performance of: Object.fromEntries vs Reduce (reuse object) vs Reduce (creating temporary objects) vs Map

Created: one year ago by: Guest

Jump to the latest result

Object.fromEntries

Reduce (reuse object)

Reduce (creating temporary objects)

Map

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):