Benchmark: JavaScript spread operator vs Object.assign vs mutation performance #2

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);
Using mutation
const finalObject = { sampleData: 'Hello world' } finalObject.moreData = 'foo bar'

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

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

Fastest: N/A

Slowest: N/A

Latest run results:

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

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Let's dive into the benchmark.

**What is being tested?**

MeasureThat.net is testing the performance of three different approaches to merge two objects in JavaScript:

1. **Spread Operator (`...`)**: This syntax allows you to merge two objects by spreading their properties into a new object.
2. **Object.assign()**: This method creates a new object and copies all enumerable own properties from one or more source objects into the new object.
3. **Mutation** (directly modifying an existing object): This approach involves assigning the values of another object to specific properties of an existing object.

**Options compared**

The benchmark is comparing these three approaches in terms of performance, which means we're interested in how quickly each method can merge two objects.

**Pros and Cons of each approach:**

1. **Spread Operator (`...`)**:
	* Pros: concise and readable syntax, creates a new object without modifying the original one.
	* Cons: may incur overhead due to function call and property iteration.
2. **Object.assign()**:
	* Pros: widely supported, efficient way to create a new object by copying properties from another object.
	* Cons: requires explicit method call, may not be as concise or readable as the spread operator.
3. **Mutation** (directly modifying an existing object):
	* Pros: can be faster if you're working with objects that already have the desired properties, and you don't need to create a new object.
	* Cons: modifies the original object, can lead to unexpected side effects if not used carefully.

**Library usage**

There is no explicit library mentioned in the benchmark definition. However, `Object.assign()` uses the built-in `Object` constructor, which is part of the JavaScript standard library.

**Special JS features or syntax**

The spread operator (`...`) was introduced in ECMAScript 2018 (ES2018) and has since become a widely supported feature across modern browsers.

**Other alternatives**

If you need to merge two objects, other alternatives include:

* Using `reduce()` with an initial value
* Creating a new object with `Object.create()`
* Using a library like Lodash (`_.merge()`)
* Using a functional programming approach with `immer` or similar libraries

Keep in mind that the choice of method depends on your specific use case, performance requirements, and personal preference.

Related benchmarks:

JavaScript spread operator vs Object.assign vs mutation performance #2 (version: 0)

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

Created: 3 years ago by: Guest

Jump to the latest result

Using the spread operator

Using Object.assign

Using mutation

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):