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
for (var i=10000; i > 0; i--) { const keys = Object.keys(obj); for (const key of keys) { 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:

Run details: (Test run date: 4 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/83.0.4103.116 Safari/537.36 Edg/83.0.478.58

Browser/OS: Chrome 83 on Windows

View result in a separate tab

Test name	Executions per second
for-in	0.9 Ops/sec
Object.keys	1.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what is being tested.

**Benchmark Definition**

The benchmark definition is a JSON object that contains information about the test case. It has three main sections:

*   **Name**: A unique identifier for the benchmark.
*   **Description**: An optional description of the benchmark (not used in this example).
*   **Script Preparation Code**: The code that sets up the environment for the benchmark. In this case, it creates an object `obj` with 11 properties, all initialized to 1.

**Individual Test Cases**

The benchmark has two individual test cases:

1.  **for-in**
    *   **Benchmark Definition**: A JavaScript loop using a traditional `for-in` loop to iterate over the properties of the `obj` object.
2.  **Object.keys**
    *   **Benchmark Definition**: A JavaScript loop using the `Object.keys()` method to get an array of property names from the `obj` object, and then iterating over that array.

**Options Compared**

The two test cases compare the performance of traditional `for-in` loops versus the `Object.keys()` method for iterating over an object's properties. The primary difference between these approaches is how they access the object's properties:

*   **For-in**: This approach uses a special syntax to iterate directly over the object's property names, without accessing their values.
*   **Object.keys()**: This approach returns an array of strings representing the property names in the object and then iterates over that array using a `for...of` loop or another iteration method.

**Pros and Cons**

Here are some pros and cons for each approach:

### For-in

Pros:

*   **Native performance**: The for-in loop is a native JavaScript construct, so it's likely to be optimized by the browser engine.
*   **Less overhead**: Since it directly accesses property names without values or keys, there might be less overhead compared to using Object.keys().

Cons:

*   **Limited iteration order**: The properties are iterated in the order they appear in the object, which can lead to issues if you need a specific order (e.g., alphabetical).
*   **Property access overhead**: Even though it directly accesses property names, there might still be some overhead due to the internal workings of the loop.

### Object.keys()

Pros:

*   **Clearer iteration order**: The properties are iterated in the order they appear as keys in the object.
*   **More flexible iteration**: You can use a `for...of` loop or other iteration methods to handle the array returned by Object.keys() more flexibly.

Cons:

*   **Array creation overhead**: Creating an array of property names has some overhead compared to directly accessing them with for-in.
*   **Browser engine implementation**: The performance may depend on the browser engine's implementation, which might not be optimized for this specific use case.

**Library Usage**

There is no library explicitly mentioned in the benchmark. However, if you're interested in exploring libraries that can simplify your JavaScript development, some popular ones include:

*   Lodash: Provides a range of utility functions to make your code more concise and readable.
*   Ramda: Offers functional programming principles and a set of immutable data structures to improve performance.

**Special JS Feature or Syntax**

There is no special JavaScript feature or syntax explicitly mentioned in the benchmark. However, if you're interested in exploring modern JavaScript features like:

*   **Async/await**: A more readable way to handle asynchronous code using promises.
*   **Classes and inheritance**: Define new classes and inherit behavior from existing ones.

These are advanced topics, but they can improve your coding efficiency and readability.

**Alternatives**

If you're looking for alternative approaches or tools to measure the performance of your JavaScript code, consider:

*   **Benchmarking libraries**: Such as BenchmarkJS or jsperf, which provide more features and flexibility in measuring performance.
*   **Performance optimization techniques**: Explore methods like code splitting, lazy loading, caching, and minimizing unnecessary computations to improve performance.

Keep in mind that each approach has its strengths and weaknesses, so it's essential to choose the right tool for your specific needs.

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>

Experimental features:

Fastest: N/A

Slowest: N/A

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