Benchmark: JavaScript spread operator vs Object.assign (with empty object parameter)

Tests:

Spread Operator
const firstObj = { id: 1, code: "1" }; const secondObj = { id: 2, code: "2" }; const finalObj = { ...firstObj, ...secondObj };
Object.assign (with empty object parameter)
const firstObj = { id: 1, code: "1" }; const secondObj = { id: 2, code: "2" }; const finalObj = Object.assign( {}, firstObj, secondObj );

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Spread Operator
Object.assign (with empty object parameter)

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/14.1.1 Safari/605.1.15

Browser/OS: Safari 14 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Spread Operator	8274645.5 Ops/sec
Object.assign (with empty object parameter)	1975256.2 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down what is being tested in the provided JSON benchmark.

The test compares two approaches to merge objects in JavaScript: the spread operator (`...`) and `Object.assign()`. Specifically, it tests using an empty object as the initial value for `Object.assign()`.

**Options Compared**

1. **Spread Operator (`...`)**: This syntax was introduced in ECMAScript 2018 (ES8) and allows you to create a new object by spreading the properties of one or more source objects into a target object.
2. **`Object.assign()` with an empty object parameter**: In this approach, an empty object is passed as the first argument to `Object.assign()`, which serves as the target object for the merge operation.

**Pros and Cons**

1. **Spread Operator (`...`)**:
	* Pros: concise, readable, and expressive syntax.
	* Cons: performance might be slightly worse due to the creation of a new object.
2. **`Object.assign()` with an empty object parameter**:
	* Pros: can be more efficient than creating a new object when using an existing object as the target.
	* Cons: less readable and less expressive syntax.

In general, the spread operator is considered a better choice due to its readability and conciseness. However, in certain performance-critical scenarios, using `Object.assign()` with an empty object parameter might be a better option.

**Other Considerations**

Both approaches are widely supported by modern browsers and JavaScript engines. When deciding which approach to use, consider the trade-off between readability, conciseness, and performance.

It's worth noting that both approaches can also be used without an initial target object (e.g., `...` with two objects or `Object.assign()` without any arguments). In those cases, the behavior is slightly different:

* Spread operator: creates a new object with the properties of all source objects.
* `Object.assign()` without arguments: throws an error if no target object is provided.

**Library and Special Features**

None mentioned in the provided benchmark. No libraries are used in this test case.

**Other Alternatives**

If you need to merge objects but don't want to use the spread operator or `Object.assign()`, consider using:

* **`Object.create()`**: creates a new object with the specified prototype.
* **`Array.prototype.reduce()`**: can be used to merge objects by accumulating properties from multiple sources into a single object.
* **Custom implementation**: you can write your own custom function to merge objects, which might provide more control over the merging process.

Keep in mind that these alternatives may not offer better performance or readability compared to the spread operator and `Object.assign()` with an empty object parameter.

Related benchmarks:

JavaScript spread operator vs Object.assign (with empty object parameter) (version: 0)

Comparing performance of: Spread Operator vs Object.assign (with empty object parameter)

Created: 3 years ago by: Guest

Jump to the latest result

Spread Operator

Object.assign (with empty object parameter)

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):