Benchmark: lodash merge vs object.assign vs spread overwriting one property

HTML Preparation code:


<script src='https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.5/lodash.min.js'></script>

Tests:

lodash merge
var a = { a: 'oh', b: 'my' }; var c = _.merge({a:true}, a);
object.assign
var a = { a: 'oh', b: 'my' }; var c = Object.assign({a:true}, a);
spread
var a = { a: 'oh', b: 'my' }; var c = { a:true, ...a };

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
lodash merge
object.assign
spread

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/119.0.0.0 Safari/537.36

Browser/OS: Chrome 119 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
lodash merge	6155501.0 Ops/sec
object.assign	12627836.0 Ops/sec
spread	40911312.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what is being tested.

**Benchmark Overview**

The benchmark measures the performance of three different approaches to merge objects in JavaScript: `_.merge` from Lodash, `Object.assign`, and spread operator (`...`). The test creates two objects, `a` and `b`, with some common properties. Then, it defines a new object `c` using each of these methods.

**Options Compared**

The benchmark compares the performance of three approaches:

1. **_.merge` from Lodash**: This method merges two objects into one, overwriting any common properties.
2. **`Object.assign`**: This method copies all enumerable own properties from one or more source objects to a target object.
3. **Spread operator (`...`) with overwrite**: This method uses the spread operator to create a new object and then assigns the `a` object to it, overwriting any common properties.

**Pros and Cons**

* **_.merge` from Lodash:**
	+ Pros:
		- Simple and concise syntax
		- Can handle nested objects
	+ Cons:
		- May be slower than other approaches due to overhead of function call and argument validation
* `Object.assign`:**
	+ Pros:
		- Fast and efficient
		- Supports shallow copying of arrays and functions
	+ Cons:
		- Less readable syntax for complex merge scenarios
		- Does not handle nested objects well
* Spread operator (`...` with overwrite):**
	+ Pros:
		- Modern and concise syntax
		- Can handle nested objects (in modern browsers that support it)
	+ Cons:
		- May not work in older browsers or environments without object spread syntax
		- Can be less readable for complex merge scenarios

**Library**

The benchmark uses the Lodash library, which provides a `merge` function to merge two objects into one. This library is widely used and well-regarded in the JavaScript community.

**Special JS Feature/Syntax**

* The benchmark uses the spread operator (`...`) with overwrite syntax, which was introduced in ECMAScript 2018 (ES2018) as part of the Object Spread Operator (Spread Syntax) feature. This syntax allows you to create a new object and then assign an existing object to it using the spread operator.

**Other Alternatives**

If you're interested in exploring other alternatives for merging objects, here are some options:

* **`Object.assign()` with nested objects**: You can use `Object.assign()` recursively by calling it on each property of the source object.
* **Merges libraries like `merge-deep` or `lodash.merge Deep`**: These libraries provide more advanced merge functionality that handles nested objects and other edge cases.
* **Custom implementation using `for...in` loop**: You can write a custom implementation using a `for...in` loop to iterate over the properties of both objects and assign values to the new object.

Related benchmarks:

lodash merge vs object.assign vs spread overwriting one property (version: 0)

Comparing performance of: lodash merge vs object.assign vs spread

Created: 6 years ago by: Guest

Jump to the latest result

lodash merge

object.assign

spread

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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