Benchmark: For in vs Object.keys.forEach vs. Object.keys+for

Script Preparation code:

var obj = new Object()
var keys = (new Array(100)).fill(0).map((x, i) => { return i + 1 })
keys.forEach((x) => { obj['prop' + x] = x })

Tests:

For In
for (var key in obj) { if (obj.hasOwnProperty(key)) console.log(obj[key]) }
Object keys forEach
Object.keys(obj).forEach(key => console.log(obj[key]))
For(;;) over Object.keys using keys.length
for (let i = 0, keys = Object.keys(obj); i < keys.length; i++) { console.log(obj[keys[i]]); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
For In
Object keys forEach
For(;;) over Object.keys using keys.length

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 27 days ago):

LLMs can make mistakes. Check important info.

The provided JSON represents a JavaScript microbenchmark test case on the MeasureThat.net website. The benchmark tests three different approaches to iterate over an object's properties: `for` loop, `Object.keys()` with `forEach()`, and using `Object.keys()` and indexing into the array directly.

**Approach 1: For In Loop**

This approach uses a traditional `for` loop to iterate over the object's properties. The loop iterates over each property in the object using `var key in obj`, and checks if the property is owned by the object using `if (obj.hasOwnProperty(key))`. This approach is simple and straightforward.

Pros:

* Easy to understand and implement
* Works well for most use cases

Cons:

* Can be slower than other approaches, especially for large objects
* May not work correctly in some browsers or environments that don't support the `hasOwnProperty()` method

**Approach 2: Object.keys() with forEach()**

This approach uses the `Object.keys()` method to get an array of the object's properties, and then passes a callback function using `forEach()` to iterate over the properties. The callback function logs each property value to the console.

Pros:

* Fast and efficient
* Works well for most use cases

Cons:

* Requires a modern JavaScript environment that supports `Object.keys()`
* May not work correctly in older browsers or environments

**Approach 3: For(;;) over Object.keys using keys.length**

This approach uses a traditional `for` loop to iterate over the array of properties returned by `Object.keys()` directly. The loop iterates from 0 to the length of the array, and logs each property value to the console.

Pros:

* Fast and efficient
* Works well for most use cases

Cons:

* Requires a modern JavaScript environment that supports array indexing
* May not work correctly in older browsers or environments

Other alternatives to these approaches include using `for...of` loops, which are more modern and concise. However, they may not be supported by older browsers or environments.

**Library and Special JS Features**

None of the benchmark test cases rely on any external libraries or special JavaScript features beyond those mentioned above. The `Object.keys()` method is a built-in part of the JavaScript standard library.

**Other Considerations**

When choosing an approach, consider the following factors:

* Performance: If speed is critical, Approach 2 (`Object.keys() with forEach()`) may be the fastest.
* Browser support: If you need to run this code in older browsers or environments, you may need to use a fallback approach (e.g., Approach 1 `For In Loop`).
* Readability and maintainability: Approach 3 (`For(;;) over Object.keys using keys.length`) is often considered more readable than the other approaches.

Ultimately, the choice of approach depends on your specific requirements and constraints.

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/92.0.4515.131 Safari/537.36

Browser/OS: Chrome 92 on Windows

View result in a separate tab

Test name	Executions per second
For In	2228.1 Ops/sec
Object keys forEach	2102.8 Ops/sec
For(;;) over Object.keys using keys.length	2324.4 Ops/sec

Related benchmarks:

For in vs Object.keys.forEach vs. Object.keys+for (version: 0)

Comparing performance of: For In vs Object keys forEach vs For(;;) over Object.keys using keys.length

Created: 3 years ago by: Guest

Jump to the latest result

For In

Object keys forEach

For(;;) over Object.keys using keys.length

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 27 days ago):