Benchmark: real for-in vs object.keys

Script Preparation code:

var obj = {
  'a': 1,
  'b': 1,
  'c': 1,
  'd': 1,
  'e': 1,
  'f': 1,
  'g': 1
};

Tests:

for-in
let c=0; for (var i=1000000; i > 0; i--) { for (var key in obj) { c++; } }
Object.keys
let c=0; for (var i=1000000; i > 0; i--) { let list=Object.keys(obj); let l=list.length; for(let ii=0;ii<l;ii++){ c++; } }

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

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 provided benchmark and explain what's being tested, compared options, pros and cons, and other considerations.

**Benchmark Purpose:**
The main goal of this benchmark is to compare the performance of two different approaches for iterating over an object in JavaScript:

1. Using a traditional `for...in` loop.
2. Using the `Object.keys()` method to get an array of the object's keys.

**Comparison Options:**

Option 1: Traditional `for...in` Loop
```javascript
for (var i = 1000000; i > 0; i--) {
  for (var key in obj) {
    c++;
  }
}
```
Option 2: Using `Object.keys()` method
```javascript
let list = Object.keys(obj);
let l = list.length;
for(let ii=0;ii<l;ii++){
  c++;
}
```
**Pros and Cons:**

* Traditional `for...in` Loop:
	+ Pros:
		- Can be more readable for simple cases.
		- Less memory usage, as it only iterates over the object's properties, not an array.
	+ Cons:
		- May have performance issues due to slow property iteration.
		- Can lead to unexpected behavior if used with objects that have inherited properties.
* Using `Object.keys()` method:
	+ Pros:
		- Faster execution, as it uses a native array-like object under the hood.
		- More predictable and robust than traditional loops.
	+ Cons:
		- Requires an extra step to get the length of the keys array.
		- May use more memory, as it creates an additional array.

**Library Usage:**
There is no explicit library usage in this benchmark. However, the `Object.keys()` method is a part of the ECMAScript standard and is implemented natively by most JavaScript engines.

**Special JS Feature/Syntax:**
This benchmark does not use any special features or syntax that would be unique to modern JavaScript versions (e.g., arrow functions, async/await, etc.).

**Other Considerations:**

* The test case uses a simple object with 10 properties and iterates over it 1 million times.
* The `c++` statement is used as the increment operation for the counter variable.
* The benchmark is executed on Chrome Mobile 96, running on Android.

**Alternatives:**
If you're looking for alternative approaches to iterate over objects in JavaScript, consider using:

* Array.prototype.forEach(): This method iterates over an array of keys and values, making it a convenient option when working with objects that are converted to arrays.
* Object.entries() and Array.prototype.forEach(): This combination provides a similar performance profile to the `Object.keys()` method while offering more flexibility in terms of iterating over both key-value pairs and individual keys.

In conclusion, this benchmark aims to compare the performance of two traditional approaches for iterating over objects in JavaScript. The results can help developers make informed decisions about which approach to use depending on their specific use cases and performance requirements.

Related benchmarks:

real for-in vs object.keys (version: 0)

Comparing performance of: for-in vs Object.keys

Created: 4 years ago by: Guest

Jump to the latest result

for-in

Object.keys

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):