Benchmark: for-in vs object.keys mensheviks

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

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

LLMs can make mistakes. Check important info.

Let's break down what's being tested in this benchmark.

The goal of this benchmark is to compare the performance of two approaches for iterating over an object: `for-in` and `Object.keys`.

**For-in loop**

The `for-in` loop is used to iterate over an object's properties. In this case, the loop iterates from 10000 down to 1 without any changes in the loop variable.

In a traditional `for-in` loop, you have three variables: `var i`, `obj[key]` (the property being iterated), and `key`. However, since the inner loop is empty, we're not using the values of `obj[key]` or `key`.

The pros of using `for-in` in this case are:

* Simplistic code: The outer loop only increments a counter without any changes.
* Easy to read and maintain: The intent is clear that we're iterating over an object.

However, there are some cons:

* Not as efficient: JavaScript engines can use optimized mechanisms to skip certain iterations of the loop when using `Object.keys`.
* Can lead to unexpected behavior if not used carefully: If you try to access or modify a property inside the loop, it may affect subsequent iterations.

**Object.keys()**

The alternative approach is using `Object.keys()` with the `forEach` method. This will also iterate over an object's properties.

In this case, we're simply logging each key to the console in ascending order from 10000 down to 1.

Pros:

* More efficient: Modern JavaScript engines can optimize `Object.keys()` to skip unnecessary iterations.
* Robust and secure: Using a standardized method like `Object.keys()` ensures consistency across browsers and devices.

Cons:

* Less readable for some developers (more verbose)
* Requires more setup (you need to initialize the loop counter)

**Other considerations**

When using `for-in`, you should be aware that if you modify an object's property inside the loop, it can lead to unexpected behavior. In this case, since the inner loop is empty, we're not concerned about modifying properties.

If you were using a more complex scenario with nested loops or conditional statements, the performance differences between `for-in` and `Object.keys()` might be negligible.

**Library:**

There is no explicit library used in this benchmark. However, modern JavaScript engines often rely on internal optimizations that allow for efficient iteration over objects.

**Special JS feature/syntax:**

There are no special features or syntax used in this benchmark that require specific knowledge of the underlying engine. The focus is on comparing two different approaches to iterating over an object.

Related benchmarks:

for-in vs object.keys mensheviks (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):