Benchmark: JavaScript spread operator vs Object.assign

Script Preparation code:

var firstObject = Array.from({ length: 100 }).reduce((acc, _el, index) => {
  acc[`some_${index}`] = index; 
  return acc;
}, {});
var secondObject = Array.from({ length: 100 }).reduce((acc, _el, index) => {
  acc[`some_other_${index}`] = index; 
  return acc;
}, {});

Tests:

Using the spread operator
const finalObject = { ...firstObject, ...secondObject };
Using Object.assign
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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**Overview of the Benchmark**

The provided JSON represents a JavaScript microbenchmarking test on MeasureThat.net, which compares the performance of two approaches: using the spread operator (`...`) and `Object.assign()` to merge two objects.

**Benchmark Definition**

The benchmark definition is divided into two parts:

1. **Script Preparation Code**: This code generates two sample objects, `firstObject` and `secondObject`, each containing 100 properties with increasing indices.
2. **Html Preparation Code**: There is no HTML preparation code provided, which means that the benchmark only focuses on JavaScript performance.

**Test Cases**

There are two individual test cases:

1. **Using the spread operator**: This test case creates a new object `finalObject` by spreading `firstObject` and then spreading `secondObject` into it.
2. **Using Object.assign**: This test case creates a new object `finalObject` by using `Object.assign()` to merge `firstObject` and `secondObject`.

**Options Compared**

The two options being compared are:

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

**Pros and Cons of Each Approach**

1. **Using the spread operator (`...`)**
	* Pros:
		+ Cleaner and more readable syntax
		+ Faster execution time, as it avoids the overhead of function calls and object property lookups
	* Cons:
		+ May not be compatible with older browsers or environments that do not support the spread operator
2. **Using Object.assign()**
	* Pros:
		+ Wide browser support and compatibility
		+ Can be used in older browsers and environments that do not support the spread operator
	* Cons:
		+ Less readable syntax, as it involves function calls and object property lookups

**Library Used**

There is no explicit library mentioned in the benchmark definition or test cases. However, `Array.from()` is a built-in JavaScript method used to create an array from an iterable.

**Special JS Feature/Syntax**

The spread operator (`...`) is a recent addition to JavaScript (introduced in ECMAScript 2015). It allows for concise object merging and spreading.

**Other Alternatives**

If the spread operator is not supported, other alternatives for object merging include:

* Using `Object.assign()` with multiple arguments
* Using `Object.create()` and then setting properties on the resulting object
* Writing a custom function for object merging

Note that these alternatives may have different performance characteristics compared to the spread operator and `Object.assign()`.

Related benchmarks:

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

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

Created: 5 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):