Benchmark: Object assign vs spread operator benchmark

Script Preparation code:

var numbers = [...Array(10).keys()]
var alphabets = [...'abcdefghijklmnopqrstuvwxyz']
var obj1 = { ...numbers }
var obj2 = { ...alphabets }

Tests:

assign
var result = Object.assign(obj1, obj2);
spread operator
var result = { ...obj1, ...obj2 };

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
assign
spread operator

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 benchmark and its test cases.

**Benchmark Purpose**

The benchmark is designed to compare two approaches for assigning properties from one object to another: `Object.assign()` and the spread operator (`{ ... }`).

**Options Compared**

Two options are compared:

1. **Object.assign()**: This method copies the enumerable properties of source objects to a target object. It's a built-in JavaScript method that has been around since the early days of the language.
2. **Spread Operator ({ ... })**: This is a relatively new feature introduced in ECMAScript 2015 (ES6). The spread operator allows you to copy the properties of an object by spreading its key-value pairs into another object.

**Pros and Cons**

**Object.assign():**

Pros:

* Widespread support across browsers and platforms
* Well-established and widely used in JavaScript development

Cons:

* Can be slower due to the overhead of creating a new object and iterating over the properties
* May not work as expected if the source objects contain non-enumerable properties or if the target object is not a plain object

**Spread Operator:**

Pros:

* Fast and efficient, as it only copies the enumerable properties from the source object to the target object
* Modern and widely adopted in JavaScript development

Cons:

* May not work across all browsers and platforms (e.g., older versions of Internet Explorer)
* Can lead to unexpected behavior if not used carefully (e.g., when dealing with non-enumerable properties or objects with inherited properties)

**Library Used**

None, as both options are native to JavaScript.

**Special JS Feature/Syntax**

The spread operator is a relatively new feature introduced in ES6. It's also known as the "Rest Operator" or "Spread Syntax."

**Other Alternatives**

If you need to assign properties from one object to another, but don't want to use either `Object.assign()` or the spread operator, you can consider using:

* **Lodash's _.assign()**: A popular utility library that provides a more convenient and expressive way to assign properties.
* **Merges** libraries: There are several libraries available that provide a simpler and more efficient way to merge objects, such as `merge-deep` or `merge-objects`.

In summary, the benchmark compares two widely used approaches for assigning properties from one object to another: `Object.assign()` and the spread operator. The spread operator is generally faster but may not work across all browsers and platforms, while `Object.assign()` has wider support but may be slower and more prone to errors.

Related benchmarks:

Object assign vs spread operator benchmark (version: 0)

Comparing performance of: assign vs spread operator

Created: 5 years ago by: Guest

Jump to the latest result

assign

spread operator

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):