Benchmark: Iterate over 2 object with merge 2

Script Preparation code:

var o1 = {};
var o2 = {};

for(var i=0; i<5000; i++) {
  o1[`id${i}`] = {i};
  o1[`id${i}2`] = {i};
}
const out = {}

var assignIn = (key) => {
    out[key] = {}
    Object.assign(out[key], o1[key], o2[key])
}

Tests:

for..in with hasOwnProperty()
for (const key in o1) { if (o1.hasOwnProperty(key)) { assignIn(key) } } for (const key in o2) { if (o2.hasOwnProperty(key)) { assignIn(key) } }
Object.keys() + Array.forEach()
Object.keys(o1) .concat(Object.keys(o2)) .forEach(assignIn)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for..in with hasOwnProperty()
Object.keys() + Array.forEach()

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 28 days ago):

LLMs can make mistakes. Check important info.

I'll break down the provided benchmark and explain what's being tested, compared options, pros and cons of each approach, library usage, special JavaScript features, and other considerations.

**Benchmark Definition JSON**

The provided JSON represents a benchmark definition for a JavaScript microbenchmark. Here's a summary:

* The benchmark is called "Iterate over 2 object with merge 2".
* It involves creating two objects (`o1` and `o2`) with a large number of properties (50,000) using a loop.
* For each property, an assignment is made to the `out` object using the `assignIn` function. The `assignIn` function merges the values from `o1` and `o2` into the `out` object for a given key.

**Benchmark Preparation Code**

The provided preparation code defines:

* Two empty objects (`o1` and `o2`) that will be populated with properties.
* A loop that iterates 50,000 times to create properties on `o1` and `o2`.
* An assignment function `assignIn` that takes a key as an argument and merges the values from `o1` and `o2` into the `out` object for that key.

**Individual Test Cases**

There are two individual test cases:

1. **Test Case 1: "for..in with hasOwnProperty()"**
	* The benchmark definition is a loop that iterates over the properties of `o1` using `for...in`. For each property, it calls the `assignIn` function if the property exists in both `o1` and `o2` using `hasOwnProperty()`.
	* This approach uses the legacy `for...in` loop with the `hasOwnProperty()` method to filter properties.
2. **Test Case 2: "Object.keys() + Array.forEach()"**
	* The benchmark definition is a loop that concatenates the keys of `o1` and `o2` using `Object.keys()`, and then iterates over the resulting array using `Array.forEach()` to call the `assignIn` function for each key.
	* This approach uses modern JavaScript's `Object.keys()` method and `Array.forEach()` to iterate over properties.

**Options Compared**

The two test cases compare:

* **Legacy `for...in` loop with `hasOwnProperty()` vs. Modern `Object.keys()` + `Array.forEach()`**
	+ Legacy `for...in` loop:
		- Pros: Wide browser support, simple syntax.
		- Cons: Performance can be slower due to the overhead of checking `hasOwnProperty()`.
	+ Modern `Object.keys()` + `Array.forEach()`:
		- Pros: Faster execution performance, more concise syntax.
		- Cons: Requires modern JavaScript features and may not work in older browsers.

**Library Usage**

There is no explicit library usage mentioned in the benchmark definition or preparation code. However, it's worth noting that some libraries like Lodash may provide optimized versions of these operations (e.g., `_.forEach()`) that could be used in a real-world scenario.

**Special JavaScript Features**

The only special feature mentioned is the use of modern JavaScript features like `Object.keys()` and `Array.forEach()`. These are part of ECMAScript 2015 (ES6) and are widely supported by modern browsers. The legacy `for...in` loop with `hasOwnProperty()` is still used in some older browsers that don't support these newer features.

**Other Considerations**

* **Browser Support**: The benchmark uses a Chrome browser, but it's likely that other browsers will be tested as well.
* **Platform and Device**: The benchmark is run on a Windows desktop platform, which may not represent all possible scenarios (e.g., mobile devices).
* **Execution Count**: The benchmark measures executions per second, which can provide insights into the performance of different approaches.

**Alternatives**

Some alternative approaches that could be considered for this benchmark include:

* Using `for...of` loop instead of `Object.keys()` and `Array.forEach()`
* Using a library like Lodash to optimize the assignment process
* Using a different data structure (e.g., arrays) instead of objects
* Adding more properties to `o1` and `o2` to increase complexity

Latest run results:

Run details: (Test run date: 6 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.100 Safari/537.36

Browser/OS: Chrome 69 on Windows

View result in a separate tab

Test name	Executions per second
for..in with hasOwnProperty()	58.2 Ops/sec
Object.keys() + Array.forEach()	67.1 Ops/sec

Related benchmarks:

Iterate over 2 object with merge 2 (version: 1)

Comparing performance of: for..in with hasOwnProperty() vs Object.keys() + Array.forEach()

Created: 6 years ago by: Registered User

Jump to the latest result

for..in with hasOwnProperty()

Object.keys() + Array.forEach()

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 28 days ago):