Benchmark: for-in vs object.keys (2)

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

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:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (X11; Linux x86_64; rv:133.0) Gecko/20100101 Firefox/133.0

Browser/OS: Firefox 133 on Linux

View result in a separate tab

Test name	Executions per second
for-in	2.3 Ops/sec
Object.keys	2.3 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

LLMs can make mistakes. Check important info.

Measuring the performance of two different approaches to iterate over an object's keys in JavaScript can be a fascinating benchmark.

**What is being tested?**

The provided JSON represents a microbenchmark that compares the performance of two methods:

1. `for-in` loop
2. Using the `Object.keys()` method

Both methods are used to log each key-value pair of an object (`obj`) containing 10000 properties.

**Options compared:**

Two options are being compared in this benchmark:

### for-in Loop

* **Approach:** The traditional JavaScript way of iterating over an object's properties using a `for-in` loop.
* **How it works:** The `for-in` loop iterates over the object's own enumerable properties, and the variable `key` takes on the value of each property in turn.

### Object.keys()

* **Approach:** Using the `Object.keys()` method to get an array of an object's own enumerable property names.
* **How it works:** `Object.keys()` returns an array of strings representing the property names of the given object. The loop then iterates over this array using a `for` loop.

**Pros and Cons:**

### for-in Loop

Pros:

* Well-supported in most browsers
* Can be used with other data structures, like arrays

Cons:

* Performance can be slow due to the loop overhead
* May not work as expected if the object has inherited properties or non-enumerable properties
* Not suitable for large datasets, as it uses a linear search approach

### Object.keys()

Pros:

* Fast and efficient, especially when compared to `for-in`
* Works well with modern JavaScript engines that optimize this method

Cons:

* May not work in older browsers that don't support the `Object.keys()` method
* Requires an additional array lookup, which can be slower than a simple loop

**Library:**

In both cases, no library is explicitly mentioned. However, it's worth noting that some libraries, like Lodash or Underscore.js, may provide optimized versions of these methods.

**Special JavaScript feature/syntax:**

There are no special features or syntax used in this benchmark. The focus is solely on comparing the performance of two iteration approaches.

**Other alternatives:**

In addition to `for-in` and `Object.keys()`, there are other ways to iterate over an object's properties, such as:

* Using a `forEach()` loop with a callback function
* Using the `Array.prototype.forEach()` method (which can be used on an array of property names)
* Using modern JavaScript features like `for...of` loops or `map()`

However, these alternatives are not being tested in this specific benchmark.

Overall, this microbenchmark provides valuable insight into the performance differences between two common iteration methods in JavaScript.

Related benchmarks:

for-in vs object.keys (2) (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

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):