Benchmark: for-in vs object.keys (fork)

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--) { const arr = [] for (const key in obj) { arr.push(obj[key]) } console.log(arr.length) }
Object.keys
for (var i=10000; i > 0; i--) { const arr = [] Object.keys(obj).forEach(key => arr.push(obj[key])); console.log(arr.length) }

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 dive into the explanation of what is tested in this benchmark.

**Benchmark Overview**

The provided JSON represents a JavaScript microbenchmark, where two test cases are compared: `for-in` and `Object.keys`. The benchmark aims to measure the performance difference between these two approaches when iterating over an object.

**Tested Options**

Two options are being compared:

1. **For-in loop**: This is an older method of iterating over an object's properties using a loop that iterates over the object's enumerable properties.
2. **Object.keys() method**: This is a modern method introduced in ECMAScript 5, which returns an array-like object containing the property names of the specified object.

**Pros and Cons**

Here are some pros and cons associated with each approach:

* **For-in loop**:
	+ Pros: Can handle objects with non-enumerable properties.
	+ Cons: Can be slower due to the overhead of checking if a property is enumerable, and it's less readable in modern code.
* **Object.keys() method**:
	+ Pros: Faster and more readable than for-in loops. It also provides additional benefits like being able to iterate over non-enumerable properties using the `String` function.
	+ Cons: Can throw an error if the object is not enumerable, which might not be the expected behavior in all cases.

**Library/Functionality Used**

In this benchmark, the `Object.keys()` method is used, which is a built-in JavaScript function. It's part of the ECMAScript standard and doesn't require any external libraries.

**Special JS Feature/Syntax**

There are no special features or syntax used in these test cases beyond what's already mentioned (i.e., the use of for-in loops and Object.keys() method).

Now, let's talk about alternatives:

Other approaches to iterate over an object could be:

* Using a `for` loop with the `in` operator: `for (var key in obj) { /* loop body */ }`
* Using a regular expression: `var keys = Object.keys(obj); var len = 0; for (var i = 0; i < keys.length; i++) { /* loop body */ }`

However, these alternatives are not as efficient or readable as using the `Object.keys()` method.

**Other Considerations**

When choosing between these approaches, consider factors like performance, readability, and compatibility with different browsers and versions. In general, `Object.keys()` is a good choice when iterating over objects in modern JavaScript code, while for-in loops might still be used in older or legacy codebases where the benefits of Object.keys() are not as well understood.

In summary, this benchmark aims to measure the performance difference between using a for-in loop and the `Object.keys()` method when iterating over an object. The results will provide insights into which approach is faster and more efficient on modern JavaScript engines.

Related benchmarks:

for-in vs object.keys (fork) (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):