Benchmark: For in vs Object.*.forEach vs Object.values 2

Script Preparation code:

var obj = new Object()
var keys = (new Array(10000)).fill(0).map((x, i) => { return i + 1 })
keys.forEach((x) => { obj['prop' + x] = x })

Tests:

For In
const arr = []; for (const key in obj) { arr.push(obj[key]); }
Object values
const arr = Object.values(obj);
Object keys for of
const arr = []; for (const key of Object.keys(obj)) { arr.push(obj[key]); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
For In
Object values
Object keys for of

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 5 months ago)

User agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:127.0) Gecko/20100101 Firefox/127.0

Browser/OS: Firefox 127 on Ubuntu

View result in a separate tab

Test name	Executions per second
For In	2418.2 Ops/sec
Object values	12333.5 Ops/sec
Object keys for of	1434.5 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and its test cases.

**Benchmark Overview**

The benchmark is designed to compare three approaches for iterating over an object: `for-in`, `Object.values()`, and `Object.keys()` with the `for...of` loop. The goal is to determine which approach provides the best performance in JavaScript.

**Options Compared**

1. **For-In**: This traditional method uses the `in` operator to iterate over the object's own enumerable properties. It can also include inherited properties, which may impact performance.
2. **Object.values()**: This method returns an array of the object's own property values without including inherited properties. It is a more modern and efficient approach.
3. **Object.keys()` with `for...of` loop**: This method uses the `Object.keys()` function to get an array of the object's own enumerable property names, and then iterates over this array using a `for...of` loop.

**Pros and Cons of Each Approach**

1. **For-In**:
	* Pros: Wide browser support, easy to understand.
	* Cons: May include inherited properties, can be slower due to the need to check for property existence.
2. **Object.values()**:
	* Pros: Efficient, modern approach that doesn't include inherited properties.
	* Cons: Requires ES6+ compatibility, may not work in older browsers.
3. **Object.keys()` with `for...of` loop**:
	* Pros: Similar to `Object.values()`, but allows for more control over property iteration.
	* Cons: May require more browser support due to the use of `Object.keys()`.

**Library and Special JS Features**

None are mentioned in the provided benchmark.

**Other Considerations**

When choosing an approach, consider the following factors:

* Browser support: If you need to support older browsers, `for-in` might be a better choice.
* Performance: `Object.values()` is generally faster due to its optimized implementation.
* Code readability and maintainability: `for...of` loop can make code more concise and readable.

**Alternatives**

Other approaches for iterating over objects include:

1. **Using `Array.prototype.forEach()`**: This method is similar to `for-in`, but uses an array-based iteration instead of a property-based approach.
2. **Using `Object.getOwnPropertyNames()`**: This method returns an array of all properties (including inherited) on the object, and can be used with `forEach()` or other iteration methods.

In summary, the benchmark provides a comprehensive comparison of three approaches for iterating over objects in JavaScript, highlighting their pros and cons, and providing guidance on choosing the best approach based on specific requirements.

Related benchmarks:

For in vs Object.*.forEach vs Object.values 2 (version: 0)

Comparing performance of: For In vs Object values vs Object keys for of

Created: 5 months ago by: Guest

Jump to the latest result

For In

Object values

Object keys for of

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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