Benchmark: JavaScript spread operator vs Object.assign performance for new object

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

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

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Let's break down what's being tested on the provided JSON.

**Benchmark Overview**

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

**Approaches Compared**

1. **Using the Spread Operator (`...`)**:
	* Creates a new object and copies properties from the first object (`firstObject`) using the spread operator.
	* Example code snippet: `const finalObject = { ...firstObject, ...secondObject };`
2. **Using `Object.assign()`**:
	* Creates an empty object (`{}`) as the target object for merging.
	* Uses `Object.assign()` to merge properties from both objects (`firstObject` and `secondObject`) into the target object.

**Pros and Cons of Each Approach**

1. **Using the Spread Operator (`...`)**:
	* Pros:
		+ More concise and readable code.
		+ Can handle nested objects with ease (e.g., `const finalObject = { a: { foo: 'bar' }, b: 'baz' }; const mergedObject = { ...a, c: 'qux' };`).
	* Cons:
		+ May have performance overhead due to the creation of a new object.
		+ Can be slower for very large objects or nested structures.
2. **Using `Object.assign()`**:
	* Pros:
		+ Often faster and more efficient than using the spread operator, especially for large objects.
		+ Can be more predictable in terms of performance, as it's a well-established method.
	* Cons:
		+ Code can become more verbose and less readable due to the need to create an empty object and then merge properties.

**Other Considerations**

1. **Library Usage**: Neither approach uses any external libraries or dependencies. The benchmark focuses solely on the JavaScript language features being compared.
2. **Special JS Features/Syntax**: The spread operator (`...`) is a relatively recent addition to JavaScript ( introduced in ECMAScript 2018). `Object.assign()` has been part of JavaScript since its inception.

**Other Alternatives**

For creating new objects by merging properties, other approaches exist:

1. **Using the `Object.assign()` method with an array of keys**: Instead of passing individual property names, you can pass an array of keys using the spread operator (`...`) or `Object.keys()`. For example: `const mergedObject = Object.assign({}, firstObject, ...Object.keys(secondObject).map(key => secondObject[key]));`
2. **Using a library like Lodash**: If you need to perform more complex object merging operations (e.g., handling nested objects with circular references), a library like Lodash can provide additional functionality.

Keep in mind that the choice of approach ultimately depends on your specific use case, performance requirements, and personal coding style preferences.

Related benchmarks:

JavaScript spread operator vs Object.assign performance for new object (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>

Fastest: N/A

Slowest: N/A

No previous run results

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