Benchmark: for-in vs object.keys (forEach) vs object.keys (for)

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 (const key in obj) { // Do nothing } }
Object.keys for each
for (var i=10000; i > 0; i--) { Object.keys(obj).forEach((key) => { // Do nothing }); }
Object.keys for
for (var i=10000; i > 0; i--) { const keys = Object.keys(obj) for (let a = 0; a < keys.length; a++) { // Do nothing } }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for-in
Object.keys for each
Object.keys for

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

This benchmark does not have any results yet. Be the first one to run it!

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

LLMs can make mistakes. Check important info.

I'll break down the benchmark and explain what's being tested, compared, and discussed.

**Benchmark Overview**

The benchmark is designed to compare the performance of three different approaches:

1. `for-in` loop
2. Using `Object.keys()` with `forEach()`
3. Using `Object.keys()` without `forEach()` ( manual iteration)

**Options Compared**

* **For-in loop**: This traditional way of iterating over an object's properties uses the `in` operator to check if a property is present in the object.
* **Object.keys()` with `forEach()`**: This approach uses the `Object.keys()` method to get an array of the object's property names, and then iterates over that array using `forEach()`.
* **Object.keys()` without `forEach()` ( manual iteration ): This option skips using `forEach()` and instead manually iterates over the array returned by `Object.keys()`.

**Pros and Cons**

1. **For-in loop**:
	* Pros: Simple, easy to understand, and often faster since it doesn't involve an additional function call.
	* Cons: May not be as efficient for large objects since it uses a separate iterator object.
2. **Object.keys()` with `forEach()`**:
	* Pros: More concise and expressive code compared to the traditional `for-in` loop.
	* Cons: May introduce overhead due to the additional function call, which can be slower than native iteration.
3. **Object.keys()` without `forEach()` ( manual iteration )**:
	* Pros: No additional function call overhead, making it potentially faster for large objects.
	* Cons: More verbose and error-prone code.

**Library Used**

The benchmark uses the built-in JavaScript `Object` and `Array` libraries. Specifically:

* `Object.keys()`: Returns an array of a given object's property names as strings.
* `forEach()`: A method that calls a provided function once for each element in an array.

**Special JS Feature/Syntax**

None mentioned explicitly, but the benchmark uses JavaScript syntax and features such as:

* ES6-style template literals (`\r\n` formatting)
* Function expression syntax (e.g., `(key) => {\t// Do nothing\r\n}`)
* Array iteration syntax (e.g., `for (let a = 0; a < keys.length; a++) { ... }`)

**Alternatives**

If you want to compare the performance of other iteration methods, consider using:

1. **Native array iteration**: Using the traditional `for` loop with indexing (`arr[i]`) instead of `forEach()`.
2. **Array.prototype.reduce()`: Using the `reduce()` method to iterate over an array and accumulate a result.
3. **Array.prototype.some() / Array.prototype.every()**: Using the `some()` or `every()` methods to check if any/ all elements in an array satisfy a condition.

Keep in mind that these alternatives may have different performance characteristics depending on the specific use case and JavaScript engine used.

Related benchmarks:

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

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

Created: 4 years ago by: Guest

Jump to the latest result

for-in

Object.keys for each

Object.keys for

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):