Benchmark: JavaScript spread operator vs Object.assign Corrected

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(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:

Run details: (Test run date: 4 years ago)

User agent: Mozilla/5.0 (Linux; Android 9; ONEPLUS A5010) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/79.0.3945.116 Mobile Safari/537.36

Browser/OS: Chrome Mobile 79 on Android

View result in a separate tab

Test name	Executions per second
Using the spread operator	6261063.5 Ops/sec
Using Object.assign	1034465.1 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks on MeasureThat.net.

**Benchmark Overview**

The benchmark in question compares two approaches for merging objects: the spread operator (`...`) and `Object.assign()`. The test creates three objects: `firstObject`, `secondObject`, and a final object that combines the properties of both using each approach.

**Test Cases**

There are two test cases:

1. **Using the Spread Operator**: This test case uses the spread operator to merge `firstObject` and `secondObject` into a single object.
```javascript
const firstObject = { sampleData: 'Hello world' }
const secondObject = { moreData: 'foo bar' }
const finalObject = { ...firstObject, ...secondObject }
```
2. **Using Object.assign()**: This test case uses `Object.assign()` to merge the two objects.
```javascript
const firstObject = { sampleData: 'Hello world' }
const secondObject = { moreData: 'foo bar' }
const finalObject = Object.assign(Object.assign({}, firstObject), secondObject)
```
**Options Compared**

The benchmark compares the performance of these two approaches:

1. **Spread Operator (`...`)**: This approach is a newer, more concise way to merge objects. It's supported in most modern JavaScript engines.
2. **`Object.assign()`**: This is an older method for merging objects. While still widely used, it can be less efficient than the spread operator.

**Pros and Cons**

**Spread Operator (`...`) Pros:**

* Concise and readable syntax
* Fast performance (usually comparable to `Object.assign()`)
* Supports nested objects

**Spread Operator (`...`) Cons:**

* May not work in older JavaScript engines (e.g., Internet Explorer)
* Can be slower than `Object.assign()` in very large object merges

**`Object.assign()` Pros:**

* Wide compatibility across browsers and platforms
* Can handle large object merges efficiently

**`Object.assign()` Cons:**

* Less readable syntax compared to the spread operator
* May require more memory allocation for intermediate results

**Library Used**

None. This benchmark doesn't use any external libraries.

**Special JS Feature or Syntax**

The spread operator is a relatively recent feature in JavaScript, introduced in ECMAScript 2018 (ES8). It's not mentioned in older browsers or platforms that may not support it.

**Other Considerations**

* The benchmark assumes that the objects being merged are relatively small. For very large objects, the performance difference between these approaches might be negligible.
* The use of `Object.assign()` on top of itself is likely done for clarity and readability purposes. In a real-world scenario, this would usually be simplified to just using the spread operator.

**Alternatives**

Other alternatives for merging objects in JavaScript include:

1. **Lodash's `merge()` function**: A popular utility library that provides various methods for merging objects.
2. **Immutable.js's `merge()` function**: Another popular library for working with immutable data structures, which also includes a merge function.
3. **Manual object creation and assignment**: For small, simple merges, manually creating an object with assigned properties can be a viable alternative.

Keep in mind that these alternatives might have different performance characteristics or use cases compared to the spread operator and `Object.assign()`.

Related benchmarks:

JavaScript spread operator vs Object.assign Corrected (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>

Experimental features:

Fastest: N/A

Slowest: N/A

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