Benchmark: for in / object.keys test

Script Preparation code:

var obj = {};
for(let i = 0; i < 100000; i++) {
  obj[i] = i;
};

Tests:

for in
for (var key in obj) { console.log(key); }
object.keys
Object.keys(obj).forEach(key => console.log(key));

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for in
object.keys

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmarking data and explain what is being tested, compared, and considered.

**Benchmark Overview**

MeasureThat.net provides a platform for users to create and run JavaScript microbenchmarks. The provided benchmark definition json represents two test cases:

1. "for in / object.keys test"
2. Two individual test cases: "for in" and "object.keys"

**Test Case 1: "for in / object.keys test"**

This test case is a composite of two separate tests: `for` loop and `Object.keys()` function.

* **Purpose:** The purpose of this test is to compare the performance of iterating over an object using the `for...in` loop versus the `Object.keys()` function.
* **Script Preparation Code:** A JavaScript object `obj` with 100,000 properties is created and initialized. This object will be used as a benchmarking data structure.

**Test Case 2: "for in"**

This test case measures the performance of iterating over an object using the `for...in` loop.

* **Benchmark Definition:** The code `for (var key in obj) { console.log(key); }` is executed.
* **Purpose:** This test is designed to measure the execution time of the `for...in` loop when iterating over an object.

**Test Case 3: "object.keys"**

This test case measures the performance of using the `Object.keys()` function to iterate over an array-like object (in this case, `obj`).

* **Benchmark Definition:** The code `Object.keys(obj).forEach(key => console.log(key));` is executed.
* **Purpose:** This test is designed to measure the execution time of using `Object.keys()` to iterate over an object.

**Comparison and Considerations**

The two tests compare the performance of iterating over an object using different approaches:

1. **for...in loop**: This approach has its own quirks, such as:
	* Iterating over inherited properties.
	* Handling prototype chains.
	* Being vulnerable to `Object.prototype` pollution (when modifying `obj` affects all objects in the prototype chain).
2. **Object.keys() function**: This approach is generally considered more modern and safer than the `for...in` loop, but:
	* Requires an array-like object or a JSON object.
	* May not work correctly with custom objects that don't follow the standard property naming conventions.

**Pros and Cons**

* **for...in loop**:
	+ Pros: Fast, widely supported, and easy to implement.
	+ Cons: Prone to errors due to quirks and edge cases, vulnerable to `Object.prototype` pollution.
* **Object.keys() function**:
	+ Pros: More modern, safer, and more accurate than the `for...in` loop.
	+ Cons: May not work correctly with custom objects or require additional setup.

**Library and Special JS Features**

No libraries are used in this benchmark. However, it's worth noting that MeasureThat.net is a JavaScript testing framework that uses various techniques to optimize performance, such as:

* **Micro-benchmarking**: Using short, isolated code snippets to measure performance.
* **Multi-threading**: Running multiple test cases concurrently to reduce overall execution time.

**Alternatives**

If you're interested in alternative approaches or want to explore more options for benchmarking JavaScript performance, consider the following alternatives:

1. **Benchmark.js**: A popular open-source benchmarking library that provides a robust and flexible API for measuring performance.
2. **jsperf**: Another well-known benchmarking tool that allows you to write custom tests and compare their performance.
3. **Google Benchmark**: A C++-based benchmarking library that can be used with JavaScript by compiling it to WebAssembly (WASM).

These alternatives offer more advanced features, such as:

* Support for multiple architectures (not just JavaScript)
* More comprehensive error handling
* Advanced analytics and visualization capabilities

Feel free to ask if you have any further questions or need clarification on specific aspects of the benchmark!

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/112.0.0.0 Safari/537.36

Browser/OS: Chrome 112 on Windows

View result in a separate tab

Test name	Executions per second
for in	1.5 Ops/sec
object.keys	1.6 Ops/sec

Related benchmarks:

for in / object.keys test (version: 0)

for in / object.keys test

Comparing performance of: for in vs object.keys

Created: one year ago by: Guest

Jump to the latest result

for in

object.keys

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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