Benchmark: JavaScript spread operator vs Object.assign performance test

Tests:

Using the spread operator
const firstObject = { sampleData: 'Hello world' } const secondObject = { moreData: 'foo bar' } const finalObject = { ...firstObject, ...secondObject };
Using Object.assign
const firstObject = { sampleData: 'Hello world' } const secondObject = { moreData: 'foo bar' } 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:

No previous run results

This benchmark does not have any results yet. Be the first one to run it!

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

LLMs can make mistakes. Check important info.

**Benchmark Explanation**

The provided benchmark measures the performance of two ways to create a new object by combining existing objects: using the JavaScript spread operator (`...`) and `Object.assign()`.

**Options Compared**

Two options are being compared:

1. **Using the Spread Operator**: This method uses the syntax `{ ...firstObject, ...secondObject }` to create a new object with all properties from both `firstObject` and `secondObject`.
2. **Using Object.assign()**: This method uses the function `Object.assign()` to merge two objects into one.

**Pros and Cons**

**Using the Spread Operator:**

Pros:

* More concise and expressive syntax
* Less memory allocation (only creates a new object reference)
* Can be more readable, especially for simple merges

Cons:

* May have performance issues due to the number of function calls and property lookups involved
* Not as widely supported in older browsers or with certain libraries

**Using Object.assign():**

Pros:

* Well-supported across all modern browsers and Node.js versions
* Can handle more complex merge scenarios, such as arrays and objects with nested properties
* No performance overhead for simple merges (only one function call)

Cons:

* Less concise syntax
* Requires two separate object references (`firstObject` and `secondObject`)
* May require additional memory allocation if the objects are large

**Library Usage**

None of the test cases use any external libraries.

**Special JavaScript Feature or Syntax**

The spread operator (`...`) is a relatively new feature introduced in ECMAScript 2018 (ES10). It's not supported in older browsers or with certain libraries, but it's becoming increasingly popular due to its concise syntax and expressive nature.

**Benchmark Preparation Code**

The preparation code for the benchmark is empty, which means that the benchmark starts from scratch for each test case. This allows for a clean and unbiased comparison of the two options.

**Other Alternatives**

Besides using the spread operator and `Object.assign()`, there are other ways to create new objects by combining existing ones:

* Using the `Array.prototype.concat()` method: `const finalObject = Object.assign({}, firstObject, secondObject);`
* Using a library like Lodash's `merge()` function: `import _ from 'lodash'; const finalObject = _.merge(firstObject, secondObject);`

However, these alternatives may not provide the same level of conciseness and readability as the spread operator or `Object.assign()`, and they might also introduce additional overhead due to memory allocation or library dependencies.

Related benchmarks:

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

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

Created: 6 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):