Benchmark: Object.assign vs named object

Script Preparation code:

var row = {a: '555', b: '666', c: '777', d: '888', e:'999'}
var fval = '000'

Tests:

Object.assign
var result = Object.assign(row,{f: fval})
named object
var result = {a: row.a, b: row.b, c: row.c, d: row.d, e: row.e, f: fval}

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Object.assign
named object

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:77.0) Gecko/20100101 Firefox/77.0

Browser/OS: Firefox 77 on Ubuntu

View result in a separate tab

Test name	Executions per second
Object.assign	7535321.5 Ops/sec
named object	44533424.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down what is being tested in the provided JSON benchmark.

**Benchmark Definition**

The benchmark compares two approaches to create an object with merged properties:

1. `named object`:
   - Creates an object with existing key-value pairs (`row`) and adds a new key-value pair (`fval`).
   - The resulting object has the same property names as `row`, but with the added `f` property.

2. `Object.assign()`:
   - Passes `row` as the target object.
   - Passes an object literal (`{ f: fval }`) as the source object to be merged into `row`.

**Options Compared**

The benchmark tests the performance of these two approaches:

* **named object**: The approach used in JavaScript since its inception, where a new object is created with existing properties and a new property added.
* **Object.assign()**: A modern method introduced in ECMAScript 2015 (ES6), providing an efficient way to merge objects.

**Pros and Cons**

1. **named object**
   - Pros:
     - Performance: Generally faster for small to medium-sized objects, as it avoids creating a new array of merged properties.
     - Simplicity: Easy to understand and use, especially when working with existing property names.
   - Cons:
     - Limitations: Not suitable for large objects or when you need to dynamically add properties. It also can lead to duplicate property name errors if the source object has an existing property with the same name as one in the target object.

2. **Object.assign()**
   - Pros:
     - Efficiency: Suitable for both small and large objects, including those with dynamic additions.
     - Error handling: Reduces the chance of duplicate property name issues by merging properties into the target object rather than overwriting them. However, it can also lead to unintended overwrites if not used carefully.
   - Cons:
     - Learning curve: May require understanding its usage and potential pitfalls (e.g., silently replacing existing properties).
     - Compatibility: Works well in most modern JavaScript environments but might have issues with older versions or non-standard browsers.

**Library Usage**

Neither of the approaches directly uses a library. However, `Object.assign()` is an intrinsic method of the `Object` prototype.

**Special JS Features/Syntax**

There are no special JavaScript features or syntaxes being tested in this benchmark.

**Other Alternatives**

If you're looking for alternative methods to merge objects, consider:

1. **Spread operators (`{ ... }`)**: Introduced in ECMAScript 2018 (ES2018), providing a concise and efficient way to spread object properties.
   ```javascript
var result = { ... row, f: fval };
```

2. **Array methods (`Object.entries()` and `reduce()`)**
   You can use these methods to create an object by merging objects, although it might be less readable than the other approaches.

3. **Manual looping**: Using a loop to iterate over source properties and add them to the target object is another approach, but it's generally considered less efficient and more error-prone.

In conclusion, the benchmark tests two common methods for creating an object with merged properties: named objects and `Object.assign()`. Understanding their pros and cons can help you choose the best approach depending on your specific use case.

Related benchmarks:

Object.assign vs named object (version: 0)

Comparing performance of: Object.assign vs named object

Created: 4 years ago by: Registered User

Jump to the latest result

Object.assign

named 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):