Benchmark: Object.fromEntries vs reduce vs property assignment

Script Preparation code:

var keys = Array(10000).fill(null).map((val, index) => index);

Tests:

Object.fromEntries
Object.fromEntries(keys.map((key) => [key, null]));
Reduce
keys.reduce((acc, k) => { acc[k] = null; return acc; }, {});
Property Assignment
const newObj = {}; keys.forEach((k) => { newObj[k] = null; });

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Object.fromEntries
Reduce
Property Assignment

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:132.0) Gecko/20100101 Firefox/132.0

Browser/OS: Firefox 132 on Windows

View result in a separate tab

Test name	Executions per second
Object.fromEntries	4308.3 Ops/sec
Reduce	12404.6 Ops/sec
Property Assignment	14020.3 Ops/sec

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

LLMs can make mistakes. Check important info.

The provided JSON represents a JavaScript benchmark test case on the MeasureThat.net website. The test aims to compare three different approaches for creating an object with key-value pairs: `Object.fromEntries`, `Array.prototype.reduce()`, and simple property assignment.

**Test Case Options:**

1. **`Object.fromEntries(keys.map((key) => [key, null]))`**: This method creates a new object by passing an array of key-value pairs to the `fromEntries()` function.
2. **`keys.reduce((acc, k) => { acc[k] = null; return acc; }, {})`**: This method uses the `reduce()` function to iterate over the array and assign each value to an existing property in the accumulator object (`acc`). If a key is not present in the accumulator, it creates a new property.
3. **Simple Property Assignment: `const newObj = {}; keys.forEach((k) => { newObj[k] = null; });`**: This method simply iterates over the array and assigns each value to a new property in an empty object (`newObj`).

**Pros and Cons of Each Approach:**

1. **`Object.fromEntries()`**:
	* Pros:
		+ Concise and readable syntax.
		+ Can create objects with default values for missing keys.
	* Cons:
		+ May have performance implications due to the overhead of creating an object iterator.
2. **`Array.prototype.reduce()`**:
	* Pros:
		+ Can be more efficient than `Object.fromEntries()` in some cases, especially when dealing with large arrays.
		+ Allows for flexible accumulator initialization.
	* Cons:
		+ May have a steeper learning curve due to the function signature and callback pattern.
3. **Simple Property Assignment**:
	* Pros:
		+ Lightweight and easy to understand syntax.
		+ No performance overhead from creating an object iterator.
	* Cons:
		+ Requires manual property access and management, which can be error-prone.

**Library Used:**

None of the test cases explicitly use any external libraries. However, `Object.fromEntries()` relies on the built-in `Object.fromEntries()` method introduced in ECMAScript 2019 (ES2020).

**Special JS Feature/Syntax:**

There is no special JavaScript feature or syntax used in these test cases.

**Other Alternatives:**

For creating objects with key-value pairs, other approaches might include:

1. Using a library like Lodash (`_.fromEntries()`) for more robust and flexible object creation.
2. Utilizing the `Array.prototype.forEach()` method with an object literal to create a new object property on each iteration (similar to Simple Property Assignment).
3. Employing other methods, such as `Array.prototype.map()` or `Array.prototype.filter()`, in combination with `Object.assign()` or other object creation functions.

Keep in mind that the choice of approach often depends on the specific use case, performance requirements, and personal preference.

Related benchmarks:

Object.fromEntries vs reduce vs property assignment (version: 0)

Comparing performance of: Object.fromEntries vs Reduce vs Property Assignment

Created: 3 years ago by: Guest

Jump to the latest result

Object.fromEntries

Reduce

Property Assignment

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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