Benchmark: for-in vs object.keys vs object.entries

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 => {}); }
object.entries
for (var i=10000; i > 0; i--) { Object.entries(obj).forEach(([key, value]) => {}); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for-in
Object.keys
object.entries

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.

**Overview**

MeasureThat.net is a website that allows users to create and run JavaScript microbenchmarks. The provided JSON represents a benchmark with three test cases: `for-in`, `Object.keys`, and `object.entries`. These test cases are designed to compare the performance of different approaches for iterating over an object in JavaScript.

**What is tested**

The test cases measure the performance of the following operations:

1. **`for-in`**: Iterating over an object using a traditional `for` loop with the `in` operator.
2. **`Object.keys`**: Using the `Object.keys()` method to get an array of keys from an object, and then iterating over it using the `forEach` method.
3. **`object.entries`**: Using the `Object.entries()` method to get an array of key-value pairs from an object, and then iterating over it using the `forEach` method.

**Options compared**

The three test cases are designed to compare the performance of different approaches for iterating over an object in JavaScript. The comparison is made between:

* Traditional `for-in` loop
* Using `Object.keys()` with `forEach`
* Using `object.entries()` with `forEach`

**Pros and Cons of each approach**

1. **Traditional `for-in` loop**:
	* Pros: Simple, easy to understand, and widely supported.
	* Cons: Can be slower than other approaches due to the overhead of checking each property's value.
2. **Using `Object.keys()` with `forEach`**:
	* Pros: Fast and efficient, as it avoids the overhead of checking each property's value.
	* Cons: May require additional memory allocation for the `key` variable, and can be slower than other approaches if the object is very large.
3. **Using `object.entries()` with `forEach`**:
	* Pros: Similar to using `Object.keys()`, it avoids the overhead of checking each property's value.
	* Cons: Requires support for ES6 features (e.g., `object.entries()`), which may not be widely supported.

**Library and purpose**

There is no specific library used in this benchmark. However, the use of `Object.keys()` and `object.entries()` methods relies on the built-in JavaScript object methods.

**Special JS feature or syntax**

This benchmark does not require any special JavaScript features or syntax beyond ES6 support for `object.entries()`.

**Other alternatives**

If you're interested in exploring alternative approaches, here are a few options:

* Using `for...of` loop with an iterator (e.g., `Object.keys().values()`)
* Using a library like Lodash or Underscore.js for iterating over objects
* Using a custom loop implementation using `Array.prototype.forEach()` and indexing into the object

Keep in mind that each approach has its own trade-offs, and the best choice will depend on your specific use case and performance requirements.

Related benchmarks:

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

Comparing performance of: for-in vs Object.keys vs object.entries

Created: 6 years ago by: Guest

Jump to the latest result

for-in

Object.keys

object.entries

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):