Benchmark: JavaScript spread operator vs Object.assign performance

Tests:

Using the spread operator
const firstObject = { test: 'Hello world', test1: "blah", test2: "ze" } const secondObject = { test1: 'La woopp', test2: 'te' } const finalObject = { ...firstObject, ...secondObject };
Using Object.assign
const firstObject = { test: 'Hello world', test1: "blah", test2: "ze" } const secondObject = { test1: 'La woopp', test2: 'te' } const finalObject = 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:

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

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Let's dive into explaining what's being tested in this JavaScript microbenchmark.

**Overview**

The benchmark compares the performance of two approaches to merge two objects in JavaScript: using the spread operator (`...`) and `Object.assign()`. The test creates two objects, `firstObject` and `secondObject`, with some common properties. The objective is to determine which approach is faster when merging these two objects into a single object, `finalObject`.

**Options Compared**

There are two options being compared:

1. **Using the spread operator (`...`)**: This method creates a new object by spreading the properties of `firstObject` and `secondObject` into a new object using the syntax `const finalObject = { ...firstObject, ...secondObject }`.
2. **Using `Object.assign()`**: This method creates a new object by merging the properties of `firstObject` and `secondObject` into a single object using the `Object.assign()` function.

**Pros and Cons**

**Using the spread operator (`...`)**

Pros:

* Concise and expressive syntax
* Can be more readable, especially when working with complex objects

Cons:

* May incur performance overhead due to the creation of a new object
* Not supported in older browsers (e.g., Internet Explorer)

**Using `Object.assign()`**

Pros:

* Well-supported by all modern browsers
* May be faster than the spread operator due to optimized implementations

Cons:

* Less readable syntax, especially for complex objects
* Can lead to memory leaks if not used carefully

**Other Considerations**

* **Memory allocation**: Both approaches allocate new memory for the resulting object. However, `Object.assign()` might allocate less memory since it only creates a reference to the existing objects.
* **Browser optimizations**: Firefox 59 is using an optimized implementation of `Object.assign()`, which might give it an advantage over the spread operator.

**Library/Functionality**

There's no specific library or functionality being used in this benchmark, other than the built-in JavaScript features mentioned above.

**Special JS feature/syntax**

The only special syntax being used here is the spread operator (`...`), which was introduced in ECMAScript 2018. If you're using an older version of JavaScript (e.g., ES6 or earlier), you might need to use a polyfill or an alternative approach.

**Alternatives**

If you're interested in exploring other approaches, you could try:

* Using `Object.create()` and then merging the properties
* Using a library like Lodash's `merge()` function
* Using a custom implementation that compares the performance of different merge strategies

Keep in mind that these alternatives might not be as concise or readable as the original approach, but they can provide insights into alternative solutions.

I hope this explanation helps!

Related benchmarks:

JavaScript spread operator vs Object.assign performance (version: 0)

Comparing performance of: Using the spread operator vs Using Object.assign

Created: 8 years ago by: Guest

Jump to the latest result

Using the spread operator

Using Object.assign

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):