Benchmark: for-in vs object.keys with for loop fixed

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--) { var keys = Object.keys(obj); for (var j = 0; j < keys.length; j ++) { console.log(keys[j]); } }

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):

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I'll explain the benchmark and its various components in detail.

**What is tested:**

The provided JSON represents two test cases for measuring the performance difference between using `for-in` loops and `Object.keys()` with a fixed loop in JavaScript.

Both test cases create an object `obj` with 11 properties (`'a'` to `'g'`) and iterate through its keys, logging each key to the console. The tests aim to determine which approach is faster on a specific browser and device platform (Chrome 89 on a Macintosh desktop).

**Options compared:**

Two options are compared:

1. **for-in loop**: This is an older way of iterating over object properties in JavaScript. It uses the `in` keyword to access each property, and the loop variable (`key`) takes on the value of each property name.
2. **Object.keys() with fixed loop**: This approach uses the `Object.keys()` method to get an array of a given object's own enumerable property names, and then iterates over this array using a traditional for loop.

**Pros and Cons:**

* **for-in loop**:
	+ Pros: Simple, intuitive, and widely supported.
	+ Cons: Can be slower due to the overhead of accessing each property name through `in`.
* **Object.keys() with fixed loop**:
	+ Pros: Faster than `for-in` since it avoids the overhead of accessing property names.
	+ Cons: Requires the use of `Object.keys()` and a traditional for loop, which can be more verbose.

**Library used (if applicable):**

None is explicitly mentioned in the provided JSON. However, it's worth noting that `Object.keys()` is a built-in method on many modern browsers and JavaScript engines, so no library is required to use it.

**Special JS feature or syntax:**

There are none mentioned in this benchmark definition. Both test cases use standard JavaScript features.

**Other considerations:**

* The tests only compare the performance of two specific approaches and do not account for other factors that might affect execution speed, such as CPU usage, memory allocation, or garbage collection.
* The benchmark is run on a single browser and device platform (Chrome 89 on a Macintosh desktop), which may not be representative of all users' experiences.

**Other alternatives:**

If you're interested in exploring alternative approaches to iterating over object properties, consider the following:

1. **for...of loop**: This is a newer way of iterating over iterable objects, including objects with enumerable property names.
2. **Array.prototype.forEach()**: You can convert an object's keys into an array and use `forEach()` to iterate over it.

Here's an example using the new `for...of` loop:
```javascript
for (const key in obj) {
  console.log(key);
}
```
This approach is similar to the `Object.keys()` method but avoids the need for an explicit array or traditional for loop.

Related benchmarks:

for-in vs object.keys with for loop fixed (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):