Benchmark: Create object - MeasureThat.net

Script Preparation code:

var obj = {a: 'a', b: 'b'};

Tests:

Spread
const newObj = { ...obj, c: 'c'};
Object.assign (mutate)
const newObj = Object.assign(obj, { c: 'c' });
Object.assign (new object)
const newObj = Object.assign({}, obj, { c: 'c' });

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Spread
Object.assign (mutate)
Object.assign (new object)

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

I'd be happy to explain the benchmark and its results.

**Benchmark Overview**

The provided JSON represents a JavaScript microbenchmark, which is a small program designed to measure the performance of specific code snippets. In this case, we have three test cases that compare different ways of creating an object with additional properties.

**Test Cases**

1. **Spread**: The first test case measures the performance of using the spread operator (`...`) to create a new object with merged properties.
```javascript
const newObj = { ...obj, c: 'c' };
```
2. **Object.assign (mutate)**: The second test case measures the performance of using `Object.assign()` to mutate an existing object and add new properties.
```javascript
const newObj = Object.assign(obj, { c: 'c' });
```
3. **Object.assign (new object)**: The third test case measures the performance of creating a new object using `Object.assign()` with an initial empty object (`{}`) and then merging it with the original object.
```javascript
const newObj = Object.assign({}, obj, { c: 'c' });
```
**Options Compared**

The benchmark compares three different approaches to create an object with additional properties:

1. **Spread Operator**: Uses the spread operator (`...`) to merge properties from two objects.
2. **Object.assign() (mutate)**: Uses `Object.assign()` to mutate an existing object and add new properties.
3. **Object.assign() (new object)**: Creates a new object using `Object.assign()` with an initial empty object (`{}`) and then merging it with the original object.

**Pros and Cons**

Here's a brief summary of each approach:

1. **Spread Operator**:
	* Pros: Simple, efficient, and widely supported.
	* Cons: Only works for objects that can be spread (e.g., properties that are not functions or symbols).
2. **Object.assign() (mutate)**:
	* Pros: Can mutate existing objects and is generally faster than creating a new object.
	* Cons: May modify the original object if not intended, and its performance can vary depending on the browser's implementation.
3. **Object.assign() (new object)**:
	* Pros: Creates a new object without modifying the original one, which can be beneficial for security or readability reasons.
	* Cons: May be slower than using `Object.assign()` with an existing object.

**Library and Special JS Feature**

None of these test cases use any libraries or special JavaScript features. They only rely on built-in language constructs.

**Other Alternatives**

If you're looking for alternative ways to create objects with additional properties, some other approaches include:

1. **Object.create()**: Creates a new object with the given prototype.
```javascript
const newObj = Object.create(obj);
newObj.c = 'c';
```
2. **Array.prototype.push()** and **Object.assign()**: Use an array as the initial object and push new properties onto it using `push()` and then merge it with another object using `Object.assign()`.
```javascript
const arr = [];
arr.push('a');
arr.push('b');
newObj = Object.assign({}, obj, arr);
```
Note that these alternatives may have different performance characteristics or trade-offs depending on your specific use case.

I hope this explanation helps you understand the benchmark and its results!

Latest run results:

Run details: (Test run date: 5 years ago)

User agent: Mozilla/5.0 (Windows NT 6.3; Win64; x64; rv:63.0) Gecko/20100101 Firefox/63.0

Browser/OS: Firefox 63 on Windows 8.1

View result in a separate tab

Test name	Executions per second
Spread	2588041.8 Ops/sec
Object.assign (mutate)	5209417.5 Ops/sec
Object.assign (new object)	1071711.9 Ops/sec

Related benchmarks:

Create object (version: 0)

Comparing performance of: Spread vs Object.assign (mutate) vs Object.assign (new object)

Created: 5 years ago by: Guest

Jump to the latest result

Spread

Object.assign (mutate)

Object.assign (new object)

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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