Benchmark: Object spread - MeasureThat.net

Script Preparation code:

var obj1 = { a: 1, b: 2 };
var obj2 = { b: 2, c: 3 };

Tests:

Spread
const obj3 = { ...obj1, ...obj2 };
Object.assign
const obj3 = Object.assign({}, obj1, obj2);

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:

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

LLMs can make mistakes. Check important info.

Let's break down what's being tested in this benchmark.

**What is being tested?**

The benchmark is testing two approaches to create a new object by merging two existing objects: the spread operator (`...`) and `Object.assign()`.

**Options compared:**

1. **Spread Operator (`...`)**:
	* The spread operator is a syntax introduced in ECMAScript 2018 (ES2018) that allows you to extract properties from an object and merge them into a new object.
	* This approach creates a shallow copy of the original objects, meaning that nested objects are not merged recursively.
	* The syntax is simple and concise: `const obj3 = { ...obj1, ...obj2 };`
2. **Object.assign()**:
	* `Object.assign()` is a method that returns a new object with the properties from the specified source objects.
	* This approach also creates a shallow copy of the original objects.
	* The syntax is more verbose: `const obj3 = Object.assign({}, obj1, obj2);`

**Pros and Cons:**

* **Spread Operator (`...`)**:
	+ Pros:
		- More concise syntax
		- Easier to read and write
	+ Cons:
		- May not be supported in older browsers or environments (not tested in this benchmark)
		- Creates a shallow copy, which might lead to unexpected behavior if working with nested objects
* **Object.assign()**:
	+ Pros:
		- Widely supported across browsers and environments
		- Can create a deep copy of objects if the `proto` property is preserved (not tested in this benchmark)
	+ Cons:
		- More verbose syntax
		- May not be as concise or readable

**Library usage:**

None, as both approaches are native JavaScript syntax.

**Special JS feature/syntax:**

* The spread operator (`...`) uses the **rest parameter syntax**, which was introduced in ECMAScript 2015 (ES6).
* `Object.assign()` is a standard method defined by the ECMAScript specification.

**Other considerations:**

Both approaches have their own use cases and performance characteristics. In general, the spread operator is preferred for its concise syntax, while `Object.assign()` is often used when working with older browsers or environments that don't support the spread operator.

**Alternatives:**

For creating a new object by merging two existing objects, you can also consider other approaches:

1. **Using Object.create() and Object.prototype.hasOwnProperty**: This method involves creating a new object using `Object.create()` and then adding properties to it using the `hasOwnProperty()` method.
2. **Using a library like Lodash's mergeDeep() function**: If you need more control over the merging process, libraries like Lodash provide functions that can help you achieve this.

Keep in mind that these alternatives might have their own trade-offs in terms of performance, readability, and support across browsers and environments.

Related benchmarks:

Object spread (version: 0)

Comparing performance of: Spread vs Object.assign

Created: 3 years ago by: Guest

Jump to the latest result

Spread

Object.assign

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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