Benchmark: for-in vs object.keys2

Script Preparation code:

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

Tests:

for-in
for (var i=10000; i > 0; i--) { for (var key in obj) { console.log(key); } }
Object.keys
for (var i=10000; i > 0; i--) { const keys = Object.keys(obj); for (let j = 0; j < keys.length; ++j) { const key = keys[j]; 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

Latest run results:

No previous 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 definition and test cases.

**Benchmark Definition**

The benchmark definition represents a JavaScript microbenchmark that compares the performance of two approaches: using `for...in` loop and `Object.keys()` function to iterate over an object's properties. The goal is to determine which approach is faster for this specific use case.

**Script Preparation Code**

The script preparation code defines a sample object `obj` with 11 properties, all initialized to the value 1:
```javascript
var obj = {
    'a': 1,
    'b': 1,
    'c': 1,
    'd': 1,
    'e': 1,
    'f': 1,
    'g': 1,
    'h': 1,
    'i': 1,
    'j': 1,
    'k': 1
};
```
This object is used as the input data for both test cases.

**Html Preparation Code**

The html preparation code is empty, which means that the benchmark does not use any HTML-related tests.

**Test Cases**

There are two individual test cases:

### Test Case 1: "for-in"

```javascript
for (var i=10000; i > 0; i--) {
    for (var key in obj) {
        console.log(key);
    }
}
```
This test case uses the `for...in` loop to iterate over the properties of the `obj` object. The loop iterates from `i = 10000` down to 1, and inside the loop, it logs each property name using `console.log(key)`.

### Test Case 2: "Object.keys"

```javascript
for (var i=10000; i > 0; i--) {
    const keys = Object.keys(obj);
    for (let j = 0; j < keys.length; ++j) {
        const key = keys[j];
        console.log(key);
    }
}
```
This test case uses the `Object.keys()` function to get an array of property names from the `obj` object. The loop then iterates over this array, logging each property name using `console.log(key)`.

**Library and Its Purpose**

In both test cases, no external libraries are used. However, the `Object.keys()` function is a built-in JavaScript method that returns an array of strings representing the property names of an object.

**Special JS Features or Syntax**

There are no special JavaScript features or syntax used in these test cases beyond what's already mentioned (e.g., `for...in` loop).

**Pros and Cons**

Here's a brief summary:

* **For...in Loop**
	+ Pros:
		- Simple to implement
		- Does not require extra memory allocation
	- Cons:
		- May exhibit slower performance due to the need for iteration over property names
		- May have issues with object prototype chain traversal
* **Object.keys() Function**
	+ Pros:
		- Provides a more efficient and modern way of iterating over object properties
		- Does not require iteration over property names, reducing overhead
	+ Cons:
		- Requires access to the `Object` global object
		- May have issues with older browsers that do not support `Object.keys()`

**Other Alternatives**

If you needed to benchmark different approaches for iterating over an object's properties, other alternatives could include:

* Using `for...of` loop instead of `for...in`
* Using a library like Lodash's `_.keys()` function
* Using a framework or library that provides optimized iteration methods (e.g., React's `useRef` hook)
* Implementing your own custom iterator using techniques like closures and generator functions

Keep in mind that the performance characteristics of these alternatives may vary depending on specific use cases, browsers, and JavaScript engines.

Related benchmarks:

for-in vs object.keys2 (version: 0)

Comparing performance of: for-in vs Object.keys

Created: 5 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):