Benchmark: for-in vs object.keys (callback caching)

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
const callback = key => console.log(key); for (var i=10000; i > 0; i--) { Object.keys(obj).forEach(callback); }

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):

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Let's dive into the world of JavaScript microbenchmarks on MeasureThat.net!

The provided benchmark measures the performance difference between two approaches for iterating over an object: `for-in` and `Object.keys()` with callback caching.

**What is being tested?**

In this benchmark, two test cases are compared:

1. The `for-in` loop, which iterates over an object using a traditional `for-in` loop.
2. The `Object.keys()` method with callback caching, where the `Object.keys()` method returns an array of keys, and then the `forEach()` method is used to iterate over this array.

**Options compared:**

The two options being compared are:

1. **Traditional `for-in` loop**: This approach uses a traditional `for-in` loop to iterate over the object's properties.
2. **`Object.keys()` with callback caching**: In this approach, `Object.keys()` returns an array of keys, and then the `forEach()` method is used to iterate over this array.

**Pros and Cons:**

1. **Traditional `for-in` loop**:
	* Pros: Simple, easy to understand, and widely supported.
	* Cons: Can be slower for large objects due to the overhead of iterating over properties and handling object iteration order (which can change).
2. **`Object.keys()` with callback caching**:
	* Pros: Faster than traditional `for-in` loop for large objects since it avoids the overhead of property iteration.
	* Cons: Requires knowledge of the `Object.keys()` method and how to cache its results.

**Library use:**

In this benchmark, no specific library is used. However, if we were to analyze the code further, we could note that the `forEach()` method is a part of the ECMAScript standard, but in older browsers, it was not widely supported. The use of `Object.keys()` and callback caching also relies on modern JavaScript features.

**Special JS feature or syntax:**

None are explicitly mentioned in this benchmark.

**Other alternatives:**

If you're looking for alternative approaches to iterating over an object, consider the following:

1. **`for...in` with a loop**: You can use a traditional `for` loop with an index variable to iterate over the object's properties.
2. **`Array.prototype.forEach()`**: If you have an array of values associated with the object's properties, you can use `forEach()` to iterate over them.
3. **Arrow functions and `Object.keys()`**: As shown in the benchmark, arrow functions can be used as callbacks with `Object.keys()`, providing a concise way to iterate over an array of keys.

In summary, this benchmark provides valuable insights into the performance differences between two common approaches for iterating over objects in JavaScript: traditional `for-in` loops and `Object.keys()` with callback caching.

Related benchmarks:

for-in vs object.keys (callback caching) (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):