Benchmark: JavaScript spread operator vs Object.assign performance (Carl)

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);

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 dive into explaining the JavaScript microbenchmarking provided by MeasureThat.net.

**Benchmark Overview**

The benchmark compares two approaches to merge objects in JavaScript: the spread operator (`...`) and `Object.assign()`. The test case consists of two individual tests, each with a brief description of the approach being tested.

**Options Compared**

1. **Spread Operator (`...`)**: This syntax is used to create a new object by copying all enumerable own properties from one or more source objects into a new object. In this benchmark, the spread operator is used to merge two objects, `firstObject` and `secondObject`, into a single object, `finalObject`.
2. **`Object.assign()`**: This method returns a shallow copy of all enumerable own properties of a given source object or an array of source objects.

**Pros and Cons**

* **Spread Operator (`...`)**:
	+ Pros: concise syntax, easy to read and write, supports nested objects and arrays.
	+ Cons: can be slower than `Object.assign()` for large datasets, as it creates a new object and copies all properties, including inherited ones.
* **`Object.assign()`**:
	+ Pros: efficient for large datasets, as it only copies enumerable own properties, and is optimized for performance.
	+ Cons: less readable and more verbose syntax compared to the spread operator.

**Library and Special JS Features**

In this benchmark, no external libraries are used. However, JavaScript 13 introduced a new feature called "Rest parameter propagation" (ECMAScript Language Specification, section 9.5), which affects the behavior of the spread operator. In JavaScript 13 and later, the spread operator can propagate rest parameters to its parent scope, making it more powerful than before.

**Other Considerations**

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

* If you need to merge objects with nested structures, the spread operator might be a better choice due to its ability to copy all properties.
* For large datasets, `Object.assign()` is generally faster, but it may not work as expected if you're trying to merge objects with non-enumerable properties.

**Alternative Approaches**

Other approaches for merging objects include:

1. **`Object.assign()` with a nested object**: You can use `Object.assign()` in combination with the spread operator to merge objects recursively.
2. **Recursive function**: Write a recursive function that merges two objects and returns the result.
3. **JSON merge libraries**: Utilize external libraries like Lodash's `_.merge()` or JSON Merge Patch (JMP) for more complex object merging scenarios.

Keep in mind that each approach has its trade-offs, and choosing the right one depends on your specific use case and performance requirements.

Related benchmarks:

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

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

Created: 3 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):