Benchmark: JavaScript spread operator vs Object.assign()

Tests:

Spread
const firstObject = { sampleData: 'Hello world' } const secondObject = { moreData: 'foo bar' } const finalObject = { ...firstObject, ...secondObject };
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
Spread
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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**Benchmark Overview**

The provided benchmark measures the performance difference between two approaches in JavaScript: using the spread operator (`...`) to merge objects, and `Object.assign()` to achieve the same result.

**Options Compared**

Two options are compared:

1. **Spread Operator (`...`)**: This approach uses the spread operator to create a new object with the properties of the original objects.
```javascript
const finalObject = { ...firstObject, ...secondObject };
```
2. **Object.assign()**: This approach uses the `Object.assign()` method to merge two or more objects into a single object.

**Pros and Cons**

**Spread Operator (`...`)**

Pros:

* Concise and readable syntax.
* Creates a new object without modifying the original objects.
* Efficient for merging small to medium-sized objects.

Cons:

* Can be slower than `Object.assign()` for large objects due to the overhead of creating a new array and iterating over it.
* Not supported in older browsers (IE 11 and below).

**Object.assign()**

Pros:

* Widely supported across modern browsers, including older versions of Internet Explorer.
* Efficient for merging large objects by using the optimized `Object.prototype.toString()` method.

Cons:

* Less readable syntax compared to the spread operator.
* Creates a new object without modifying the original objects, but uses additional memory due to the creation of intermediate arrays.

**Other Considerations**

Both approaches have their trade-offs. The spread operator is more modern and concise, but may incur performance penalties for very large objects. `Object.assign()` is widely supported, but its syntax can be less readable. Additionally, both approaches do not preserve the original object's prototype chain when merging objects with a different prototype.

**Library Usage**

Neither of the compared options uses any external libraries. The spread operator is a built-in JavaScript feature introduced in ECMAScript 2018 (ES9), while `Object.assign()` has been part of the standard since ECMAScript 5 (ES5).

**Special JS Feature or Syntax**

The spread operator (`...`) introduces a new syntax for merging objects, which is relatively modern and widely adopted. It allows for more concise code and improved readability.

**Alternative Approaches**

If the performance difference between these two approaches is not significant, other options can be considered:

1. **Object.create()**: This method creates a new object with a given prototype, allowing for more control over the resulting object's properties.
```javascript
const finalObject = Object.create(firstObject.prototype)(function() {
  this.sampleData = firstObject.sampleData;
  this.moreData = secondObject.moreData;
});
```
2. **Object.assign()` with `Array.prototype.slice()`**: This approach uses `Array.prototype.slice()` to create a shallow copy of the source objects, which can be faster for large objects.
```javascript
const finalObject = Object.assign({}, Array.prototype.slice.call(Object.values(firstObject)), Array.prototype.slice.call(Object.values(secondObject)));
```
Keep in mind that these alternative approaches may have their own trade-offs and are not necessarily more efficient than the compared options.

Related benchmarks:

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

Comparing performance of: Spread vs Assign

Created: 5 years ago by: Guest

Jump to the latest result

Spread

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):