Benchmark: for-in vs object.keys true

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 (let 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:

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.

**Benchmark Explanation**

The provided JSON represents a JavaScript microbenchmark test case on the MeasureThat.net website. The benchmark compares the performance of two approaches to iterate over an object's properties:

1. **For-in loop**: This approach uses a traditional `for` loop with the `in` keyword to iterate over the object's properties.
2. **Object.keys() method**: This approach uses the built-in `Object.keys()` method to get an array of the object's property names, which is then iterated over using a `for...of` loop.

**Options Comparison**

The two approaches have different pros and cons:

* **For-in loop**:
	+ Pros: Simple, easy to understand, and widely supported.
	+ Cons: Can be slower due to the overhead of looking up property names in the object's prototype chain.
* **Object.keys() method**:
	+ Pros: More efficient, as it avoids the overhead of property name lookup. Also, it returns an array, which can be more suitable for certain use cases.
	+ Cons: Requires the `Object.keys()` method to be supported by the browser or engine being tested.

**Other Considerations**

* **Loop variables**: Both approaches use a loop variable (`i` in the traditional `for` loop and `key` in the `for...of` loop). The choice of loop variable does not affect the performance of the benchmark.
* **Object size**: The object used in the benchmark has 11 properties, which is relatively small. For larger objects, the impact of the `in` keyword lookup may become more significant.

**Library and Special JS Features**

None of the provided benchmarks use a library or special JavaScript features that would affect the interpretation of the results.

**Alternative Approaches**

If you want to explore alternative approaches for iterating over an object's properties, consider the following:

* **Array.prototype.forEach()**: This method is another way to iterate over an array (or object) and can be used in some cases where `Object.keys()` or `for-in` are not suitable.
* **Symbol iterators**: Some browsers support symbol iterators, which provide a more efficient way to iterate over objects that use symbols as property names. However, this approach is not supported by all browsers.

**Benchmark Preparation Code**

The provided script preparation code creates an object with 11 properties and assigns the value `1` to each property:
```javascript
var obj = {
  'a': 1,
  'b': 1,
  'c': 1,
  'd': 1,
  'e': 1,
  'f': 1,
  'g': 1,
  'h': 1,
  'i': 1,
  'j': 1,
  'k': 1
};
```
The HTML preparation code is empty, indicating that no specific HTML or CSS setup is required for this benchmark.

Related benchmarks:

for-in vs object.keys true (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

No previous run results

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