Benchmark: JavaScript spread operator vs Object.assign performance vs Manual assignment

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(firstObject, secondObject);
Manual assignment
const firstObject = { sampleData: 'Hello world' } const secondObject = { moreData: 'foo bar' } const finalObject = {}; finalObject.sampleData = firstObject.sampleData; secondObject.moreData = secondObject.moreData;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

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

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 JavaScript benchmark.

**What is being tested?**

The benchmark compares the performance of three different approaches to create a new object by merging two existing objects:

1. **Using the spread operator (`...`)**: This syntax uses the spread operator to create a new object with properties from both `firstObject` and `secondObject`.
2. **Using `Object.assign()`**: This function takes multiple source objects as arguments and returns a new object created by merging all the source objects.
3. **Manual assignment**: This approach involves manually assigning properties of `firstObject` to the new object, and then assigning properties of `secondObject` to the same object.

**Options compared**

The benchmark is comparing the performance of these three approaches on a desktop Windows system running Chrome 112.

**Pros and Cons of each approach:**

1. **Using the spread operator (`...`)**:
	* Pros: concise and readable syntax, efficient creation of new objects.
	* Cons: may not be supported in older browsers or environments that don't understand the spread operator.
2. **Using `Object.assign()`**:
	* Pros: widely supported across browsers and environments, easy to use and understand.
	* Cons: can create a new object with duplicate properties, which might lead to unexpected behavior if not used carefully.
3. **Manual assignment**:
	* Pros: explicit control over the creation of the new object, no dependencies on other libraries or syntax.
	* Cons: more verbose and less readable than the first two approaches.

**Library usage**

None of the test cases use any external libraries beyond what's built into JavaScript (e.g., `Object`).

**Special JS feature or syntax**

The spread operator (`...`) is a relatively recent addition to JavaScript, introduced in ECMAScript 2018. It allows you to create new objects by spreading the properties of an existing object.

**Other considerations**

To make this benchmark more comprehensive, it might be worth considering additional approaches, such as:

* Using `Object.create()` or `Object.assign()` with a target object.
* Using a library like Lodash's `merge()` function.
* Testing performance on different types of devices (e.g., mobile, tablet).

These additions would help to provide a more complete picture of the trade-offs between these approaches and ensure that the results are relevant to a broader range of use cases.

Related benchmarks:

JavaScript spread operator vs Object.assign performance vs Manual assignment (version: 0)

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

Created: 7 years ago by: Guest

Jump to the latest result

Using the spread operator

Using Object.assign

Manual assignment

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):