Benchmark: JavaScript spread operator vs Object.assign performance - forked for equivalent functionality

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:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/89.0.4389.114 Safari/537.36

Browser/OS: Chrome 89 on Linux

View result in a separate tab

Test name	Executions per second
Using the spread operator	1886636.9 Ops/sec
Using Object.assign	4248331.0 Ops/sec

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

LLMs can make mistakes. Check important info.

The provided JSON represents a JavaScript benchmark test case on MeasureThat.net, where users can create and run microbenchmarks to compare the performance of different approaches.

**Benchmark Definition:**

The benchmark tests two approaches for creating a new object by merging two existing objects:

1. Using the spread operator (`...`): This approach creates a new object and then uses the spread operator to merge the properties from `firstObject` and `secondObject`.
2. Using `Object.assign()`: This approach directly merges the properties from `firstObject` and `secondObject` into a new object.

**Options compared:**

The benchmark compares the performance of these two approaches, which are essentially creating a shallow copy of the source objects by merging their properties.

**Pros and Cons:**

1. **Using the spread operator (`...`):**
	* Pros:
		+ More concise and expressive way to merge objects.
		+ Can be faster in modern browsers due to optimized JavaScript engine optimizations.
	* Cons:
		+ May not work correctly with older browsers or environments that don't support it.
2. **Using `Object.assign()`:**
	* Pros:
		+ Works consistently across all browsers and environments.
		+ Can be useful when working with legacy codebases.
	* Cons:
		+ Less concise and may require more lines of code.

**Library usage:**

None in this benchmark.

**Special JavaScript features or syntax:**

The spread operator (`...`) is a modern JavaScript feature introduced in ECMAScript 2018 (ES2018). It allows you to expand arrays, objects, or other iterable values into a new object with the same keys and values. This feature was not available in older versions of JavaScript.

**Other alternatives:**

In the past, developers might have used other methods to merge objects, such as:

1. **For loops:** `for (key in firstObject) { finalObject[key] = firstObject[key]; }` followed by `for (key in secondObject) { finalObject[key] = secondObject[key]; }`
2. **JSON merging libraries:** Some libraries, like `lodash`, provide functions to merge objects.
3. **Object literals with multiple assignment:** `const finalObject = { ...firstObject, ...secondObject };`

However, these alternatives are generally less concise and efficient than the spread operator or `Object.assign()`.

Related benchmarks:

JavaScript spread operator vs Object.assign performance - forked for equivalent functionality (version: 0)

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

Created: 3 years ago by: Guest

Jump to the latest result

Using the spread operator

Using Object.assign

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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