Benchmark: index by id: Object.fromEntries vs reduce

Script Preparation code:

var array = Array.from({
    length: 1000
}, () => ({
    id: Math.random() * 100000 | 0,
    key1: Math.random() * 100000 | 0,
    key2: Math.random() * 100000 | 0,
    key3: Math.random() * 100000 | 0,
    key4: Math.random() * 100000 | 0
}))

Tests:

Object.fromEntries
Object.fromEntries(array.map(item => [item.id, item]))
Array.prototype.reduce
array.reduce((acc, val) => { acc[val.id] = val; return acc; }, {})

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Object.fromEntries
Array.prototype.reduce

Fastest: N/A

Slowest: N/A

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/126.0.0.0 Safari/537.36

Browser/OS: Chrome 126 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Object.fromEntries	8003.6 Ops/sec
Array.prototype.reduce	10212.3 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks.

**What is being tested?**

The provided JSON represents a benchmark test that compares two approaches for creating an index object from an array:

1. `Object.fromEntries()`
2. `Array.prototype.reduce()`

In more detail, the test creates an array of 1000 objects with random `id`, `key1`, `key2`, and `key4` properties. The benchmark then measures the execution time of two functions that create an index object from this array using the above methods.

**Options compared:**

The two options being compared are:

1. **Object.fromEntries()**: a modern JavaScript method introduced in ECMAScript 2015 (ES6) for creating an object from an array of key-value pairs.
2. **Array.prototype.reduce()**: a built-in method in the Array prototype that applies a function to each element in the array, accumulating a value.

**Pros and cons:**

* **Object.fromEntries():**
	+ Pros:
		- Concise syntax
		- Modern and widely supported
		- Can be more readable for those familiar with this method
	+ Cons:
		- May have performance overhead due to its creation of an object and pushing elements into it
		- May not be optimized for older browsers or environments
* **Array.prototype.reduce():**
	+ Pros:
		- Well-established and widely supported
		- Can be more efficient for large arrays, as it avoids creating a new object
		- Allows for more control over the accumulation process
	+ Cons:
		- More verbose syntax compared to `Object.fromEntries()`
		- May require more cognitive effort from developers familiar with this method

**Library usage:**

None of the libraries are used in this benchmark. The functions being tested (`Object.fromEntries()` and `Array.prototype.reduce()`) are part of the JavaScript language itself.

**Special JS feature or syntax:**

There is no specific JavaScript feature or syntax mentioned that's not commonly known. However, it's worth noting that `Object.fromEntries()` relies on a modern ECMAScript implementation that supports this method, whereas older browsers may not support it.

**Other alternatives:**

If you need to create an index object from an array, other alternatives could include:

1. Using the spread operator (`...`) and object literals to create a new object.
2. Utilizing libraries like Lodash or Ramda for utility functions that can help with indexing.
3. Implementing your own loop-based solution.

However, `Object.fromEntries()` is likely to be the most efficient and convenient choice in this scenario, given its concise syntax and widespread support.

I hope this explanation helps you understand the test case!

Related benchmarks:

index by id: Object.fromEntries vs reduce (version: 0)

Comparing performance of: Object.fromEntries vs Array.prototype.reduce

Created: one year ago by: Guest

Jump to the latest result

Object.fromEntries

Array.prototype.reduce

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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