Benchmark: for-in vs object.keys without stuff

Script Preparation code:

var obj = {
  'a': 1,
  'b': 2,
  'c': 3,
  'd': 4,
  'e': 5,
  'f': 6,
  'g': 7
};

Tests:

for-in
for (let i = 0; i < 10000; ++i) { for (const key in obj) { console.log(key); } }
Object.keys
for (let i = 0; i < 10000; ++i) { for (const key of Object.keys(obj)) { 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.

**Overview of the Benchmark**

The provided JSON represents a JavaScript benchmark that compares two approaches to iterate over an object's properties: `for-in` loop and using the `Object.keys()` method.

**What is being tested?**

In this benchmark, the following options are compared:

1. **`for-in` loop**: This is an older way of iterating over an object's properties in JavaScript. It uses a manual index (`key`) to access each property.
2. **`Object.keys()` method**: This is a built-in JavaScript method that returns an array of an object's own enumerable property names.

**Pros and Cons**

- **`for-in` loop**:
  - Pros: Can be used when the order of iteration matters or when you need to access both the key and value.
  - Cons: May iterate over inherited properties, which can lead to unexpected behavior. It also uses a manual index, which can be error-prone.

- **`Object.keys()` method**:
  - Pros: More concise and readable than the `for-in` loop. Does not include inherited properties in the result.
  - Cons: Requires an additional import for older browsers (prior to ECMAScript 2015). May have a slight performance overhead due to the creation of an array.

**Library**

None, as this benchmark uses only built-in JavaScript methods and does not rely on any external libraries.

**Special JS Features/Syntax**

- **ECMAScript 2015+**: The `Object.keys()` method was introduced in ECMAScript 2015 (ES6). This means that older browsers may not support it. To make this benchmark compatible with older browsers, you would need to add a polyfill or use a different approach.

**Benchmark Preparation Code**

The provided preparation code creates an object `obj` with 7 properties and assigns them integer values from 1 to 7.

**Individual Test Cases**

Two test cases are defined:

- **Test Case 1: `for-in` loop**: This test case uses a traditional `for-in` loop to iterate over the object's properties.
- **Test Case 2: `Object.keys()` method**: This test case uses the `Object.keys()` method to retrieve an array of property names, which is then iterated using a `for...of` loop.

**Latest Benchmark Result**

The benchmark was run on a Chrome browser with version 89.0.4389.82 on a Linux-based desktop device. The results are:

- **`for-in` loop**: Executed approximately 1.38 executions per second.
- **`Object.keys()` method**: Executed approximately 0.90 executions per second.

Note that the performance difference between these two approaches is relatively small, but `Object.keys()` may be slightly faster due to its optimized implementation.

**Alternatives**

Other alternatives for iterating over an object's properties include:

- Using a `for...of` loop with the spread operator (`...`) or `Array.from()`.
- Using the `for...in` loop with the `hasOwnProperty()` method to exclude inherited properties.
- Using a library like Lodash, which provides a more robust and flexible way of working with objects.

Related benchmarks:

for-in vs object.keys without stuff (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):