Benchmark: Object.assign vs Object.fromEntries

Script Preparation code:

function createArray(propsCount) {
    const arr = []
    for (let i = 0; i < propsCount; i += 1) {
        arr.push({
            active: i % 5 === 0
        })
    }
    return arr
}

var users = createArray(1000)

Tests:

Reduce
users.reduce((acc, curr) => { if (curr.active) { return acc } return { ...acc, [curr.id]: curr.name } })
Map Filter Reduce Assign
users.filter((user) => !user.active).map((user) => ({ [user.id]: user.name })).reduce(Object.assign, {})
From Entries
const a = users.filter((user) => !user.active).map((user) => [user.id, user.name]) Object.fromEntries(a)
Object Assign
Object.assign( {}, ...users.filter((user) => !user.active).map((user) => ({ [user.id]: user.name })) )

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Reduce
Map Filter Reduce Assign
From Entries
Object Assign

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 dive into the world of JavaScript benchmarks.

**Benchmark Purpose**

The provided JSON represents two benchmarking tests: `Object.assign vs Object.fromEntries` and four individual test cases (`Reduce`, `Map Filter Reduce Assign`, `From Entries`, and `Object Assign`). These tests aim to measure the performance differences between various approaches for merging or transforming objects in JavaScript.

**Comparison of Options**

Here's a brief overview of the options being compared:

1. **Object.assign**: This method copies all enumerable own properties from one object to another.
2. **Object.fromEntries**: This method creates a new object from an array of key-value pairs.
3. **Reduce**: A method that applies a function against an accumulator and each element in the array (from left to right) to reduce it to a single value.
4. **Map Filter Reduce Assign**: An operation consisting of three parts: filtering, mapping, reducing, and assigning the result to a new object using `Object.assign`.
5. **From Entries**: A method that creates a new object from an array of key-value pairs.

**Pros and Cons**

Here's a brief summary of the pros and cons for each approach:

1. **Object.assign**:
	* Pros: Simple, widely supported, and efficient.
	* Cons: Can be slow when dealing with large objects or deep properties.
2. **Object.fromEntries**:
	* Pros: Modern, concise, and efficient.
	* Cons: Less widely supported than `Object.assign`.
3. **Reduce**:
	* Pros: Flexible, allowing for custom accumulation logic.
	* Cons: Can be slower due to the overhead of function calls.
4. **Map Filter Reduce Assign**:
	* Pros: Encapsulates multiple operations in a single operation, reducing overhead.
	* Cons: More complex than individual operations, which can lead to confusion and performance issues if not optimized correctly.
5. **From Entries**:
	* Pros: Modern, concise, and efficient.
	* Cons: Less widely supported than `Object.assign`.

**Library Usage**

None of the provided benchmarks explicitly use external libraries.

**Special JS Features or Syntax**

There are no special JavaScript features or syntaxes mentioned in the provided benchmarks.

**Benchmark Preparation Code**

The preparation code for the benchmark is provided, including a custom function `createArray` to generate an array of objects with specific properties. This code is used to create the input data for each test case.

**Individual Test Cases**

Each test case measures the performance of a specific approach:

1. **Reduce**: Measures the performance of using `reduce` to merge objects.
2. **Map Filter Reduce Assign**: Measures the performance of combining multiple operations: filtering, mapping, reducing, and assigning the result.
3. **From Entries**: Measures the performance of using `Object.fromEntries` to create a new object from an array of key-value pairs.
4. **Object Assign**: Measures the performance of using `Object.assign` to merge objects.

**Latest Benchmark Results**

The latest benchmark results are provided, showing the execution per second for each test case and browser.

**Other Alternatives**

For those seeking alternative approaches or more detailed explanations, here are a few suggestions:

1. Explore other methods for merging or transforming objects, such as using `lodash` or custom utility functions.
2. Dive deeper into the implementation details of `Object.assign` and `Object.fromEntries`.
3. Investigate how modern browsers optimize object property iteration and merging.

I hope this explanation helps software engineers understand the benchmarking tests and approaches being compared!

Latest run results:

Run details: (Test run date: 8 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/121.0.0.0 Safari/537.36 OPR/107.0.0.0

Browser/OS: Opera 107 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Reduce	26707.5 Ops/sec
Map Filter Reduce Assign	24.4 Ops/sec
From Entries	34742.3 Ops/sec
Object Assign	62288.6 Ops/sec

Related benchmarks:

Object.assign vs Object.fromEntries (version: 0)

Comparing performance of: Reduce vs Map Filter Reduce Assign vs From Entries vs Object Assign

Created: 8 months ago by: Guest

Jump to the latest result

Reduce

Map Filter Reduce Assign

From Entries

Object Assign

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):