Benchmark: Object.assign vs spreading object copy

Tests:

Spread
let object = {...{foo: "bar"}}
Object.assign
let object = Object.assign({}, {foo: "bar"})

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Spread
Object.assign

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one month ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/146.0.0.0 Safari/537.36 Edg/146.0.0.0

Browser/OS: Chrome 146 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Spread	80873648.0 Ops/sec
Object.assign	40931416.0 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's being tested, compared, and the pros and cons of each approach.

**Benchmark Description**

The benchmark is comparing two ways to create a copy of an object: using the spread operator (`...`) and using `Object.assign()`.

**Options Compared**

1. **Spread Operator (`...`)**: This method creates a new object by copying the properties from an existing object. It's a concise way to create a shallow copy of an object.
2. **Object.assign()**: This method creates a new object by copying the specified properties from one or more source objects.

**Pros and Cons**

* **Spread Operator (`...`)**:
	+ Pros: Concise, easy to read, and efficient for simple cases.
	+ Cons: Creates a shallow copy, which means it only copies the top-level properties. If the object has nested objects or arrays, they won't be copied recursively.
* **Object.assign()**:
	+ Pros: More flexible, can create deep copies by using multiple source objects.
	+ Cons: Less concise and more verbose than the spread operator.

**Library and Special JS Feature**

There is no specific library being used in this benchmark. However, it's worth noting that the `...` syntax was introduced in ECMAScript 2015 (ES6) as a shorthand for creating an object from an array of key-value pairs or an existing object with spread syntax.

**Benchmark Test Cases**

The test cases are designed to compare the performance of each method:

1. **Spread Operator (`...`)**: The benchmark creates an object `object` with a single property `foo` set to `"bar"`. It then measures the time it takes to create an array of key-value pairs using the spread operator and assign it to a new variable.
2. **Object.assign()**: The benchmark creates an object `object` with a single property `foo` set to `"bar"`. It then measures the time it takes to use `Object.assign()` to create a copy of the object.

**Other Considerations**

* The benchmark is designed to test the performance of each method on a specific type of data (a simple object with one property). In more complex scenarios, the results may vary.
* The benchmark doesn't account for the overhead of function calls or other JavaScript operations that might affect performance.

**Alternative Approaches**

If you need to create a deep copy of an object, you can use libraries like Lodash's `cloneDeep()` or Underscore's `clone()`. Alternatively, you can use recursive functions to create a deep copy by copying each nested property individually.

For more complex scenarios or performance-critical code, you may want to consider using just-in-time (JIT) compilation or other optimization techniques specific to your JavaScript engine.

Related benchmarks:

Object.assign vs spreading object copy (version: 0)

Comparing performance of: Spread vs Object.assign

Created: 5 years ago by: Guest

Jump to the latest result

Spread

Object.assign

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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