Benchmark: JavaScript spread operator vs Object.assign performance with New Object Twice

Tests:

Using the spread operator
const firstObject = { sampleData: 'Hello world' } const secondObject = { moreData: 'foo bar' } const finalObject = { ...firstObject, ...secondObject };
Using Object.assign
const firstObject = { sampleData: 'Hello world' } const secondObject = { moreData: 'foo bar' } const finalObject = Object.assign(Object.assign({}, firstObject), secondObject);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Using the spread operator
Using Object.assign

Fastest: N/A

Slowest: N/A

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

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Let's break down what's being tested in this benchmark and the pros and cons of the approaches used.

**Benchmark Overview**

The benchmark compares the performance of two ways to create a new object by merging two existing objects: using the spread operator (`...`) and using `Object.assign()`. The test cases create two objects, `firstObject` and `secondObject`, with different properties, and then attempt to merge them into a single object.

**Options Compared**

1. **Spread Operator (`...`)**:
	* Pros:
		+ Concise and expressive syntax.
		+ Easy to read and understand for developers familiar with the spread operator.
		+ Can be used to create objects with any number of properties.
	* Cons:
		+ May not be as efficient as `Object.assign()` in all cases, especially when dealing with large objects or nested properties.
		+ Can lead to unexpected behavior if not used carefully (e.g., using `...` on a non-object value).
2. **Object.assign()**:
	* Pros:
		+ Well-established and widely supported method for merging objects.
		+ Can handle nested properties and large objects efficiently.
		+ Supports chaining multiple assignments.
	* Cons:
		+ Can be less concise and more verbose than the spread operator.
		+ May require more manual error handling (e.g., checking for null or undefined values).

**Library Used**

In this benchmark, `Object.assign()` is used to merge objects. `Object.assign()` is a built-in JavaScript method that copies properties from one or more source objects into a new object.

**Special JS Feature/Syntax**

The spread operator (`...`) was introduced in ECMAScript 2018 (ES10) as a proposal for a new syntax feature. It allows you to extract properties from an object and merge them with another object using the `...` symbol. This feature is widely supported by modern browsers and JavaScript engines.

**Other Considerations**

When deciding between the spread operator and `Object.assign()`, consider the following:

* If you need to merge objects frequently, `Object.assign()` might be a better choice due to its efficiency and support for nested properties.
* However, if readability and conciseness are important, the spread operator can be a good option.
* Be aware of potential pitfalls when using the spread operator, such as unexpected behavior with non-object values or nested objects.

**Alternatives**

Other alternatives for merging objects include:

* Using the `Object.create()` method to create a new object and then assigning properties to it using the spread operator or `Object.assign()`.
* Using a library like Lodash's `merge()` function, which provides additional features and flexibility.
* Implementing your own custom merge function, which can provide fine-grained control over the merging process.

In summary, this benchmark compares the performance of two ways to create a new object by merging two existing objects. The spread operator offers a concise and expressive syntax, while `Object.assign()` is more efficient and widely supported for merging large or nested objects.

Related benchmarks:

JavaScript spread operator vs Object.assign performance with New Object Twice (version: 0)

Comparing performance of: Using the spread operator vs Using Object.assign

Created: 4 years ago by: Guest

Jump to the latest result

Using the spread operator

Using 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):