Benchmark: object.assing vs spread

Script Preparation code:

var xs = {};
for (let i = 0; i < 1000000; i++) {
  xs[`h${i}`] = `h${i}`;
}

Tests:

spread
var xs2 = {...window.xs};
object.assign
var xs3 = Object.assign({}, window.xs);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
spread
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):

LLMs can make mistakes. Check important info.

Let's break down the benchmark and its components.

**Benchmark Definition**

The test measures the performance of two approaches to assign values to an object in JavaScript: using the spread operator (`...`) and `Object.assign()` method.

**Options Compared**

Two options are compared:

1. **Spread Operator**: The spread operator is used to create a new object by spreading the properties of an existing object. In this benchmark, the spread operator is used to assign values to the `xs` object.
2. **Object.assign() Method**: The `Object.assign()` method is used to copy the properties of one or more source objects into a target object.

**Pros and Cons**

* **Spread Operator:**
	+ Pros:
		- More concise and expressive syntax
		- Less boilerplate code required
		- Can be more readable for simple assignments
	+ Cons:
		- May have performance overhead due to the creation of a new object
		- Can lead to unexpected behavior if not used carefully (e.g., modifying the original object)
* **Object.assign() Method:**
	+ Pros:
		- More explicit and controlled syntax
		- Easier to manage complex assignments or merge objects with multiple sources
		- Less prone to unexpected behavior due to its explicit nature
	+ Cons:
		- More verbose code required compared to the spread operator
		- May lead to more maintenance issues if not used carefully

**Library and Purpose**

The `Object.assign()` method is a built-in JavaScript method that has been part of the language since ECMAScript 2015 (ES6). Its primary purpose is to copy properties from one or more source objects into a target object.

**Special JS Feature/Syntax**

This benchmark does not use any special JavaScript features or syntax beyond what is standard in ES6 and later versions. It only relies on the basic JavaScript language features mentioned earlier.

**Other Alternatives**

If you want to explore alternative approaches, you could consider:

1. Using the `for...in` loop with the `=` operator: `var xs = {}; for (var prop in window.xs) { xs[prop] = window.xs[prop]; }`
2. Using a library like Lodash's `cloneDeep()` function: `const _ = require('lodash'); var xs2 = _.cloneDeep(window.xs);`

Keep in mind that these alternatives may not have the same performance characteristics as the spread operator and `Object.assign()` method.

**Benchmark Preparation Code**

The script preparation code creates a large object `xs` with 1 million properties, each initialized to the string "h${i}", where `i` ranges from 0 to 999,999. This creates a resource-intensive scenario for benchmarking.

**Individual Test Cases**

Each test case measures the performance of either the spread operator or `Object.assign()` method when creating a new object by copying the properties of an existing object (`window.xs`). The tests run in succession, comparing their execution times and reporting back to MeasureThat.net.

Related benchmarks:

object.assing vs spread (version: 0)

Comparing performance of: spread vs object.assign

Created: 4 years ago by: Guest

Jump to the latest result

spread

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):