Benchmark: assign vs spread test inside loop v2

Tests:

assign
const a = { title: 'asd' } for (let i = 0; i < 1000; i++) { Object.assign(a, {[i]: i}) }
spread
let a = { title: 'asd' }; for (let i = 0; i < 1000; i++) { a = { ...a, [i]: i } }
property assign
let a = { title: 'asd' }; for (let i = 0; i < 1000; i++) { a[i] = i }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
assign
spread
property assign

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/124.0.0.0 Safari/537.36

Browser/OS: Chrome 124 on Windows

View result in a separate tab

Test name	Executions per second
assign	513.1 Ops/sec
spread	2908.4 Ops/sec
property assign	106908.1 Ops/sec

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

LLMs can make mistakes. Check important info.

I'd be happy to explain the benchmark and its various aspects.

**Benchmark Overview**

The provided JSON represents a JavaScript microbenchmark test case, specifically designed to compare the performance of three different approaches for assigning values to an object within a loop.

**Test Cases**

There are three individual test cases:

1. **assign**: This test case uses `Object.assign()` to assign new properties to the existing object `a`. The benchmark is run in a loop 1000 times, where each iteration assigns a new property `[i]: i` to `a`.
2. **spread**: This test case uses the spread operator (`...`) to create a shallow copy of the object `a`, and then updates the newly created object with the additional properties using the syntax `{ ...a, [i]: i }`. The benchmark is run in a loop 1000 times, where each iteration creates a new object with the updated properties.
3. **property assign**: This test case simply assigns values directly to existing properties of `a` using the syntax `a[i] = i`. The benchmark is run in a loop 1000 times.

**Options Compared**

The three test cases compare the performance of:

1. Using `Object.assign()` for property assignment (test case **assign**)
2. Using the spread operator (`...`) for creating and updating an object (test case **spread**)
3. Directly assigning values to existing properties (test case **property assign**)

**Pros and Cons**

*   **Assign**: This approach can be beneficial when you need to append new properties to an existing object, as it avoids issues with property names being overwritten.
    However, this method is not suitable for large objects due to its performance overhead, as `Object.assign()` creates a shallow copy of the target object.
*   **Spread**: The spread operator is efficient and convenient when you need to create new objects by copying existing properties. However, it can be slower than direct property assignment if the number of properties being assigned is small, since it involves creating a new object with the added properties.
    Additionally, spreading an object can introduce additional overhead due to the creation of a temporary object.
*   **Property Assign**: This approach is simple and efficient for assigning values directly to existing properties. However, it may not be suitable when dealing with large numbers of properties or when you need to append new properties to an existing object.

**Library/Features Used**

None mentioned in the provided benchmark definition.

**Special JS Features/Syntax**

The spread operator (`...`) is a relatively recent feature introduced in ECMAScript 2018 (ES2018). It allows creating new objects by copying existing properties and adding new ones.

Note that if you're targeting older browsers or environments, you might need to use polyfills or fallbacks for the spread operator.

**Alternatives**

If you don't want to use `Object.assign()` or the spread operator, you could consider using libraries like Lodash or underscore.js, which provide similar functionality. However, keep in mind that these libraries may introduce additional overhead and dependencies.

Alternatively, you could implement your own custom solution for property assignment, but this would likely be less efficient and less convenient than using established libraries or built-in features like `Object.assign()` or the spread operator.

Related benchmarks:

assign vs spread test inside loop v2 (version: 0)

Comparing performance of: assign vs spread vs property assign

Created: 2 years ago by: Registered User

Jump to the latest result

assign

spread

property assign

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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