Benchmark: test forin vs keys+foreach

HTML Preparation code:

<!--your preparation HTML code goes here-->

Script Preparation code:

  let temp = {
  "surname": "Verdi",
  "name": "Giovanni",
  "cfPiva": "VRDGVN90C12E567Z",
  "plate": "IJ789KL",
  "birthDate": "1990-10-20",
  "proviceBirth": "Torino",
  "cityBirth": "Torino",
  "proviceResidence": "Torino",
  "cityResidence": "Torino",
  "company": "LMN Srl",
  "mainRole": "Ingegnere",
  "roles": "Sviluppatore, Progettista",
  "injuries": "Nessuno"
};let imports={};

Tests:

for in test
for (const key in temp) { imports[key] = "true"; }
keys+foreach
Object.keys(temp).forEach(key => { imports[key] = "true"; });

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for in test
keys+foreach

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36

Browser/OS: Chrome 131 on Windows

View result in a separate tab

Test name	Executions per second
for in test	3529745.5 Ops/sec
keys+foreach	3176668.2 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated one year ago):

LLMs can make mistakes. Check important info.

The provided JSON represents a benchmark focused on comparing two different approaches to iterate over the properties of an object in JavaScript: using a `for...in` loop and using `Object.keys()` in combination with the `forEach` method.

### Benchmark Description

1. **Test Cases**:
   - **For...in Loop**:
     ```javascript
     for (const key in temp) {
         imports[key] = "true";
     }
     ```
     This loop iterates over enumerable properties of the `temp` object. Each key is assigned a value of `"true"` in the `imports` object.

- **Object.keys() + forEach**:
     ```javascript
     Object.keys(temp).forEach(key => {
         imports[key] = "true";
     });
     ```
     This approach first retrieves an array of the object's own enumerable property names (keys) using `Object.keys()`, and then iterates over that array with `forEach`. It performs the same assignment as the `for...in` loop.

### Performance Results

The benchmark results indicate the number of executions per second for each test case as follows:
- **For...in Test**: 3,529,745.5 executions per second.
- **Keys + forEach Test**: 3,176,668.25 executions per second.

### Pros and Cons

- **For...in Loop**:
  - **Pros**:
    - Simple and straightforward syntax.
    - Operates directly over the object's enumerable properties without creating an intermediate array.
  - **Cons**:
    - Can include properties from the prototype chain if not used with caution (i.e., checking with `hasOwnProperty`). This can potentially lead to unexpected results when working with objects that inherit properties.

- **Object.keys() + forEach**:
  - **Pros**:
    - Only iterates over the object’s own properties (not inherited), which avoids potential pitfalls associated with prototype properties.
    - Clearer in intent: it explicitly indicates we are using only the own keys of the object.
  - **Cons**:
    - Slight overhead from creating an intermediate array with `Object.keys()`.
    - Potentially less performant than `for...in`, particularly in scenarios with large sets of properties, depending on the JavaScript engine's optimization capabilities.

### Other Considerations

- **Use Cases**: The choice between these methods may depend on the context. For most cases where performance is critical, benchmarking in specific environments (like this case demonstrates) is essential to making informed decisions.
- **Alternatives**:
  - **forEach** alone does not work on arrays derived from arrays, but if you're iterating through an array of objects, `Array.prototype.map()` or a simple `for` loop might be considered for clearer syntax and potentially better performance.
  - **for...of Loop**: While not directly applicable here since `for...of` works with iterable objects (like arrays), using `Array.entries()` or `Array.keys()` could also be considered when working with arrays of objects.

In summary, this benchmark illustrates the performance implications of two common JavaScript approaches for iterating over object properties, providing insights into how choice of iteration method can impact execution speed and code clarity.

Related benchmarks:

test forin vs keys+foreach (version: 1)

Comparing performance of: for in test vs keys+foreach

Created: one year ago by: Guest

Jump to the latest result

for in test

keys+foreach

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated one year ago):