Benchmark: JavaScript spread operator vs Object.assign performance up

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

Latest run results:

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

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**What is being tested?**

The provided benchmark measures the performance difference between using the JavaScript spread operator (`...`) and `Object.assign` to merge two objects into a single object.

**Options compared:**

Two approaches are being compared:

1. **Using the spread operator**: This method uses the spread operator (`...`) to create a new object by copying properties from the first object (`firstObject`) and then merging them with properties from the second object (`secondObject`). The syntax is:
```javascript
const finalObject = { ...firstObject, ...secondObject };
```
2. **Using `Object.assign`**: This method uses the `Object.assign` method to merge two objects into a single object. The syntax is:
```javascript
const finalObject = Object.assign({}, firstObject, secondObject);
```
**Pros and Cons of each approach:**

1. **Using the spread operator**:
	* Pros:
		+ More concise and readable syntax.
		+ Can be faster since it only creates a new object reference, rather than creating a new object and then assigning properties to it.
	* Cons:
		+ Only works with objects that support spreading (i.e., objects with enumerable properties).
		+ May not be as efficient for very large objects due to the overhead of copying properties.
2. **Using `Object.assign`**:
	* Pros:
		+ More flexible and widely supported since it's a built-in method on the `Object` prototype.
		+ Can handle large objects more efficiently since it can use native methods like `Map` and `Set`.
	* Cons:
		+ Less concise and less readable syntax compared to the spread operator.
		+ May be slower due to the overhead of creating a new object and assigning properties to it.

**Library:**

In this benchmark, no libraries are being used beyond the built-in JavaScript methods (`Object.assign`).

**Special JS feature or syntax:**

The spread operator is a relatively recent feature introduced in ECMAScript 2018. It's available in most modern browsers, but not all older browsers support it.

**Other alternatives:**

Alternative approaches to merge two objects include:

1. **Object.create()**: This method creates a new object using the `Object.create()` constructor, which is then assigned properties.
```javascript
const finalObject = Object.create(null);
finalObject.sampleData = 'Hello world';
finalObject.moreData = 'foo bar';
```
2. **For...in loop**: This method uses a for-in loop to iterate over the properties of one object and assigns them to another object.
```javascript
const finalObject = {};
for (const prop in firstObject) {
  if (firstObject.hasOwnProperty(prop)) {
    finalObject[prop] = firstObject[prop];
  }
}
finalObject.moreData = secondObject.moreData;
```
These alternatives may have different performance characteristics and are not as concise or readable as the spread operator or `Object.assign`.

Related benchmarks:

JavaScript spread operator vs Object.assign performance up (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):