Benchmark: for in Object.keys vs foreach Object.keys

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 Object.keys
const keys = Object.keys(obj); for (let i = 0; i < keys.length; i += 1){ console.log(keys[i]); }
foreach Object.keys
Object.keys(obj).forEach(function(key) { console.log(key); });

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for in Object.keys
foreach Object.keys

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):

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Let's break down the provided benchmark and explain what's being tested, compared options, pros and cons, and other considerations.

**Benchmark Overview**

The benchmark is designed to compare the performance of two approaches for iterating over object keys in JavaScript: `for` loop with `Object.keys()` and `forEach()` method. The test aims to determine which approach is faster and more efficient.

**Script Preparation Code**

The script preparation code creates an object `obj` with 10,000 properties, where each property is assigned a value from 1 to 10,000 using the `fill()`, `map()`, and `forEach()` methods. The resulting object has keys ranging from 1 to 10,000.

**Html Preparation Code**

There is no HTML preparation code provided for this benchmark.

**Benchmark Definition**

The benchmark definition consists of two test cases:

1. **"for in Object.keys"`**: This test case uses a traditional `for` loop with the `Object.keys()` method to iterate over the object's keys.
2. **"foreach Object.keys"`**: This test case uses the `forEach()` method with `Object.keys()` to iterate over the object's keys.

**Comparing Options**

The two approaches differ in how they access and manipulate the object's keys:

* **`for in Object.keys()`**: This approach iterates over the keys using an indexed loop, where each iteration returns a key-value pair.
* **"foreach Object.keys"`**: This approach uses `forEach()` to iterate over the keys without indexing. Instead, it receives a callback function that takes only one argument, the key value.

**Pros and Cons**

Here's a summary of the pros and cons of each approach:

* **`for in Object.keys()`**:
	+ Pros: Can access object properties by index (e.g., `obj['prop1']`) and is more familiar to many developers.
	+ Cons: May be slower due to indexing, as it needs to look up each property individually.
* **"foreach Object.keys"`**:
	+ Pros: More concise and expressive code, as it avoids explicit looping and indexing.
	+ Cons: May not be as readable for some developers, especially those without experience with `forEach()`.

**Special JavaScript Features/Syntax**

There are no special JavaScript features or syntax used in this benchmark beyond the standard `Object.keys()`, `for` loops, and `forEach()` method.

**Other Alternatives**

If you're interested in alternative approaches, consider:

1. Using a library like Lodash's `mapKeys()` function to iterate over object keys without indexing.
2. Employing a loop that uses bitwise operations to access properties directly (e.g., `obj[0x01]`).
3. Utilizing the `Array.prototype.keys()` method (introduced in ECMAScript 2019) to access object keys.

Keep in mind that these alternatives may have different performance characteristics and trade-offs depending on your specific use case.

**Benchmark Results**

The latest benchmark results show that both approaches perform similarly, with Firefox 113 executing around 13-14 times per second. However, the actual performance difference might be negligible for most use cases, as the test object's size is relatively small (10,000 properties).

Related benchmarks:

for in Object.keys vs foreach Object.keys (version: 0)

Comparing performance of: for in Object.keys vs foreach Object.keys

Created: 2 years ago by: Guest

Jump to the latest result

for in Object.keys

foreach 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):