Benchmark: Object.assign vs brackets notation

Tests:

Object.assign
const firstObject = { sampleData: 'Hello world' } const secondObject = { moreData: 'foo bar' } const finalObject = Object.assign({}, firstObject, secondObject);
Brackets
const firstObject = { sampleData: 'Hello world' } let finalObject = firstObject; finalObject['moreData'] = 'foo bar';

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Object.assign
Brackets

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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Let's break down the provided benchmark and explain what's being tested.

**Benchmark Overview**

The benchmark is comparing two approaches for merging objects in JavaScript:

1. **`Object.assign()`**: A built-in method that merges properties from one or more source objects into a target object.
2. **Brackets notation**: A shorthand way of accessing object properties using square brackets `[]`.

**Options Compared**

The two options being compared are:

1. **`Object.assign()`**: The official JavaScript method for merging objects. It creates a new object with the properties from the source objects and assigns them to the target object.
2. **Brackets notation**: A shorthand way of accessing object properties using square brackets `[]`. This approach is often used in modern JavaScript code, especially when working with objects.

**Pros and Cons**

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

Pros:

* Clearer intent: The method name explicitly conveys its purpose of merging objects.
* More explicit control: You can easily pass multiple source objects to the method if needed.
* Better error handling: `Object.assign()` will throw an error if one or more source objects are null or undefined.

Cons:

* Performance overhead: Creating a new object and assigning properties can be slower than using brackets notation.
* Less concise: The method requires more code compared to brackets notation.

**Brackets notation**:

Pros:

* Concise: You only need to write the property name, making it shorter and easier to read.
* Efficient: Brackets notation creates a new object with the desired properties without creating intermediate objects.

Cons:

* Less explicit control: The brackets notation can lead to confusion if not used carefully (e.g., what happens when accessing non-existent properties?).
* Error-prone: If you're not careful, you might end up with errors due to typos or missing bracket notation.

**Library and Special JS Feature**

There is no library being used in this benchmark. However, the use of brackets notation does rely on the existence of JavaScript's `Symbol` feature (specifically, the `Symbol.prototype.propertyName` method), which was introduced in ECMAScript 2015 (ES6). This feature allows you to get a string representation of the property name using the bracket notation.

**Other Alternatives**

If you prefer other approaches for merging objects, here are some alternatives:

* **Using the spread operator (`{ ... }`)**: This approach is also known as "spread syntax" and was introduced in ECMAScript 2015 (ES6). It allows you to merge objects by simply placing an object literal after the target object's name.
```javascript
const finalObject = { sampleData: 'Hello world', ...firstObject, moreData: 'foo bar' };
```
* **Using `Array.prototype.reduce()`**: This approach involves using the reduce method to accumulate properties from multiple source objects into a single target object.

For example:
```javascript
const finalObject = firstObject;
['sampleData', 'moreData'].forEach((key) => {
  if (finalObject[key] === undefined) {
    finalObject[key] = secondObject[key];
  } else {
    finalObject[key] += secondObject[key];
  }
});
```
These alternatives are often more concise and readable than using `Object.assign()` or brackets notation, but they can also be less explicit about their intent.

Related benchmarks:

Object.assign vs brackets notation (version: 0)

Comparing performance of: Object.assign vs Brackets

Created: 2 years ago by: Guest

Jump to the latest result

Object.assign

Brackets

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):