Benchmark: Object.fromEntries vs create temp object vs Array.reduce

Script Preparation code:

var array = Array.from(Array(10000).keys())

Tests:

Object.fromEntries
Object.fromEntries(array.map(value => [value, value]));
creating temporary objects
const data = {}; array.forEach(value => data[value] = value);
Array.reduce
array.reduce((obj, item) => { obj[item] = item; return obj; }, {});

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Object.fromEntries
creating temporary objects
Array.reduce

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 24 days ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/125.0.0.0 Safari/537.36

Browser/OS: Chrome 125 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Object.fromEntries	2665.3 Ops/sec
creating temporary objects	21554.4 Ops/sec
Array.reduce	20618.0 Ops/sec

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

LLMs can make mistakes. Check important info.

**Overview**

The provided JSON represents a JavaScript microbenchmark test case on the MeasureThat.net website. The benchmark compares three approaches for creating an object from an array: `Object.fromEntries`, creating a temporary object, and using `Array.reduce`. We'll break down each approach, discuss their pros and cons, and explore other alternatives.

**Approaches**

### 1. Object.fromEntries

`Object.fromEntries()` is a method introduced in ECMAScript 2017 (ES7) that creates an object from key-value pairs. In this benchmark, `Object.fromEntries(array.map(value => [value, value]))` is used to create an object where each key-value pair is derived from the array.

Pros:

* Concise and expressive code
* Well-documented and widely supported

Cons:

* May incur overhead due to method call and function creation

### 2. Creating a temporary object

This approach involves creating a temporary object using the syntax `const data = {};`. The loop then iterates over the array, assigning each value to the object using dot notation (e.g., `data[value] = value`).

Pros:

* May be faster due to direct property assignment
* Portable across older browsers and environments

Cons:

* More verbose code compared to `Object.fromEntries`
* Error-prone if not handled carefully (e.g., handling null or undefined values)

### 3. Array.reduce

The third approach uses `Array.reduce()` to create the object. In this case, `array.reduce((obj, item) => { obj[item] = item; return obj; }, {})` is used.

Pros:

* Efficient use of array iteration
* Flexibility in handling complex data structures

Cons:

* May require more memory due to intermediate object creation
* Less intuitive code compared to `Object.fromEntries`

**Library and special JS features**

In the benchmark, no libraries are explicitly mentioned. However, `Array.from()` is used to create an array from a range of numbers (1-10,000), which is not a standard JavaScript feature.

**Other considerations**

When choosing between these approaches, consider the following factors:

* Code readability and maintainability
* Performance requirements (e.g., speed, memory usage)
* Browser and environment support (older browsers or environments may not support `Object.fromEntries`)

**Alternatives**

If you're looking for alternative methods to create objects from arrays in JavaScript, here are a few options:

1. `Array.prototype.reduce()`: Similar to the third approach, but without the `Object` context.
2. `Array.prototype.forEach()`: While not suitable for creating objects directly, this method can be used with a callback function that creates an object.
3. Manual iteration using loops and array indexing (e.g., `array[index] = value;`)

Keep in mind that these alternatives may have different performance characteristics and code readability compared to the approaches mentioned above.

In conclusion, the choice of approach depends on your specific requirements, code readability preferences, and performance considerations. MeasureThat.net's benchmark can help you understand the relative performance of each approach.

Related benchmarks:

Object.fromEntries vs create temp object vs Array.reduce (version: 0)

Comparing performance of: Object.fromEntries vs creating temporary objects vs Array.reduce

Created: 3 years ago by: Guest

Jump to the latest result

Object.fromEntries

creating temporary objects

Array.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):