Benchmark: JavaScript Object.assign vs for in loop new1

Tests:

Object.assign
const objects = [{ A: 'a', B: 'b', C: 'c', D: 'd', E: 'e', F: 'f', G: 'g', H: 'h', I: 'i', J: 'j', K: 'k', L: 'l', M: 'm', }, { A: 'n', B: 'o', C: 'p', D: 'q', E: 'r', F: 's', G: 't', H: 'u', I: 'v', J: 'w', K: 'x', L: 'y', M: 'z', } ]; const target = { ...objects[0] }; Object.assign(target, objects[1]);
for in loop
const objects = [{ A: 'a', B: 'b', C: 'c', D: 'd', E: 'e', F: 'f', G: 'g', H: 'h', I: 'i', J: 'j', K: 'k', L: 'l', M: 'm', }, { A: 'n', B: 'o', C: 'p', D: 'q', E: 'r', F: 's', G: 't', H: 'u', I: 'v', J: 'w', K: 'x', L: 'y', M: 'z', } ]; const target = { ...objects[0] }; for (const key in target) { target[key] = objects[1][key]; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Object.assign
for in loop

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) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/110.0.0.0 Safari/537.36

Browser/OS: Chrome 110 on Windows

View result in a separate tab

Test name	Executions per second
Object.assign	1522238.8 Ops/sec
for in loop	1533458.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down what's being tested on the provided JSON.

**Benchmark Definition**

The benchmark is comparing two approaches to merge objects: `Object.assign` and a traditional `for...in loop`. The script preparation code creates two object literals with the same structure, but different values. It then creates a target object that only has the first set of keys (`objects[0]`) and uses either `Object.assign` or a `for...in loop` to merge the second set of key-value pairs from `objects[1]`.

**Options Compared**

There are two options being compared:

1. **`Object.assign`**: This method takes an existing object as an argument, and then merges one or more new objects into it.
2. **Traditional `for...in loop`**: This approach iterates over the properties of the target object using a `for...in loop`, and then assigns each value from the source object to the corresponding property.

**Pros and Cons**

### Object.assign

Pros:

* Concise and expressive syntax
* Fast and efficient, since it avoids the overhead of a loop
* Works well with objects that have nested properties

Cons:

* Requires the source object to be an existing object (or a collection of key-value pairs)
* Can throw errors if the target object is not an object
* May not work as expected with complex object structures or non-standard property names

### Traditional `for...in loop`

Pros:

* Flexible and customizable, allowing for more control over the merge process
* Works well with objects that have complex or non-standard properties
* Can be used in situations where `Object.assign` would throw an error (e.g., if the target object is not an object)

Cons:

* More verbose syntax compared to `Object.assign`
* Slower and less efficient than `Object.assign`, since it involves a loop
* May be more prone to errors due to the need for manual property iteration

**Library/Function Used**

In this benchmark, the library function used is `Object.assign`. It's a built-in JavaScript method that takes an existing object as an argument, and then merges one or more new objects into it.

**Special JS Feature/Syntax**

There isn't any special JavaScript feature or syntax being used in this benchmark. The focus is on comparing two simple object merge approaches.

**Other Alternatives**

If you're interested in exploring alternative object merge methods, here are a few options:

* **`Object.create()`**: This method creates a new object that inherits properties from an existing object.
* **`Array.prototype.reduce()`**: This method can be used to merge objects by reducing an array of key-value pairs into a single object.
* **ES6 `Object.reduce()`**: This method is a more concise alternative to `Array.prototype.reduce()`, but it's not yet widely supported in older browsers.

Note that each of these alternatives has its own trade-offs and use cases, so be sure to explore them further if you're interested!

Related benchmarks:

JavaScript Object.assign vs for in loop new1 (version: 0)

Comparing performance of: Object.assign vs for in loop

Created: one year ago by: Guest

Jump to the latest result

Object.assign

for in loop

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):