Benchmark: Object.defineProperty vs Object.assign

Script Preparation code:

var input = new Array(100).fill().map((v, i) => i)

Tests:

Object.defineProperty
const output = input.reduce((acc, value) => Object.defineProperty(acc, `key${value}`, { value }), {});
Object.assign (immutable)
const output = input.reduce((acc, value) => Object.assign({}, acc, { [`key${value}`]: value }), {});
Object.assign (mutable)
const output = input.reduce((acc, value) => Object.assign(acc, { [`key${value}`]: value }), {});

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Object.defineProperty
Object.assign (immutable)
Object.assign (mutable)

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 6 days ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36

Browser/OS: Chrome 131 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Object.defineProperty	63649.0 Ops/sec
Object.assign (immutable)	1646.7 Ops/sec
Object.assign (mutable)	62458.2 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the benchmark and its test cases.

**Benchmark Definition**

The benchmark is comparing three approaches for defining properties on an object:

1. `Object.defineProperty`: This method sets one or more own properties on an object, creating them if they don't exist. It can also be used to add new attributes to existing objects.
2. `Object.assign` (with mutable assignment): This method copies all enumerable own properties from one or more source objects to a target object.
3. `Object.assign` (with immutable assignment): This method creates a shallow copy of an array, which is then used as the initial value for the `acc` object in the reduction.

**Options Compared**

The benchmark is comparing the performance of these three approaches:

* **Immutable Object Assign**: Using `Object.assign` to create a new object with properties set from another object. This approach creates a new object and copies the properties, which can be slower.
* **Mutable Object Assign**: Using `Object.assign` on an existing object to add new properties. This approach modifies the original object, which can be faster since it avoids creating a new object.
* **DefineProperty**: Using `Object.defineProperty` to set properties on an object. This method creates the property if it doesn't exist and can also modify existing ones.

**Pros and Cons of Each Approach**

1. **Immutable Object Assign (with Object.assign)**:
	* Pros: Creates a new object, which can be beneficial for data protection.
	* Cons: Can be slower due to the overhead of creating a new object.
2. **Mutable Object Assign (with Object.assign)**:
	* Pros: Faster since it modifies an existing object without creating a new one.
	* Cons: May not be suitable for data protection, as changes can be lost if the original object is modified elsewhere.
3. **DefineProperty**:
	* Pros: Can set properties on an existing object and create them if they don't exist.
	* Cons: Can be slower due to the overhead of setting properties on an object.

**Library Usage**

None of the test cases use a specific library, but it's worth noting that `Object.assign` is part of the ECMAScript standard, while `Object.defineProperty` uses a proprietary method call.

**Special JS Features or Syntax**

There are no special JavaScript features or syntax used in these benchmark definitions. The focus is on comparing the performance of different object assignment approaches.

**Other Alternatives**

If you're looking for alternative ways to assign properties to an object, you could consider:

1. **Object.create()**: Creates a new object with a given prototype.
2. **Array.prototype.forEach()**: Iterates over an array and executes a callback function for each element.
3. **for...of loop**: Iterates over an iterable (e.g., an array) using a for-of loop.

However, the current benchmark is specifically focused on comparing `Object.defineProperty` with `Object.assign`, making these alternatives less relevant to this particular comparison.

Related benchmarks:

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

Comparing performance of: Object.defineProperty vs Object.assign (immutable) vs Object.assign (mutable)

Created: 4 years ago by: Guest

Jump to the latest result

Object.defineProperty

Object.assign (immutable)

Object.assign (mutable)

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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