Benchmark: for-in vs for-of and object.keys

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); } }
for-of and Object.keys
for (var i=10000; i > 0; i--) { for (var 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
for-of and 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.

Let's dive into the explanation of the provided benchmark.

**Benchmark Overview**

The benchmark measures the performance difference between two loop structures: `for-in` and `for-of with Object.keys`. The test case uses an object literal (`obj`) to demonstrate the comparison.

**Options Compared**

The benchmark compares the following options:

1. **For-in**: This traditional loop structure iterates over an object's properties using the `in` operator.
2. **For-of with Object.keys**: This modern loop structure uses the `Object.keys()` method to get an array of an object's property keys, and then iterates over it using a `for...of` loop.

**Pros and Cons**

Here are the pros and cons of each approach:

### For-in

Pros:

* Easy to implement and understand for developers familiar with older JavaScript versions.
* Can be more efficient in certain situations due to its direct access to property names.

Cons:

* Less predictable behavior when dealing with property names that contain special characters or have non-standard formatting (e.g., camelCase).
* May lead to unexpected side effects if used incorrectly (e.g., modifying the original object).

### For-of with Object.keys

Pros:

* More predictable and safer, as it only iterates over property keys without modification.
* Can handle complex property names more reliably.

Cons:

* Requires a modern JavaScript version that supports `Object.keys()` and `for...of` loops.
* May be slightly slower due to the overhead of creating an array of property keys.

**Library/Functionality Used**

In this benchmark, the following library/functionality is used:

* `Object.keys()`: A built-in JavaScript method that returns an array of a given object's property names.

**Special JS Feature/Syntax**

The test case uses the `for...of` loop syntax, which was introduced in ECMAScript 2015 (ES6). This syntax allows for more concise and expressive looping over arrays and other iterable objects.

Other Alternatives

If you'd like to explore similar benchmarks or alternatives, here are a few suggestions:

* Measure the performance of different array iteration methods (e.g., `forEach`, `map`, `reduce`) using `for` loops.
* Compare the performance of different string manipulation techniques (e.g., concatenation vs. template literals).
* Investigate the impact of code optimization techniques (e.g., minification, compression) on benchmark results.

Please let me know if you'd like more information or guidance!

Related benchmarks:

for-in vs for-of and object.keys (version: 0)

Comparing performance of: for-in vs for-of and Object.keys

Created: 3 years ago by: Guest

Jump to the latest result

for-in

for-of and 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):