Benchmark: for in vs for loop with object.keys 123

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
for (var i=10000; i > 0; i--) { let tempKeys = Object.keys(obj); let tempKeysLength = tempKeys.length; for (let x = 0; x < tempKeysLength; x++) console.log(tempKeys[x]); }

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):

LLMs can make mistakes. Check important info.

**Benchmark Overview**

MeasureThat.net is a website that allows users to create and run JavaScript microbenchmarks. The benchmark in question compares the performance of two approaches for iterating over an object's properties: `for-in` loop and using `Object.keys()`.

**Benchmark Definition JSON**

The benchmark definition JSON contains information about the test case, including:

* `Name`: A unique name for the benchmark.
* `Description`: An optional description of the benchmark (not provided in this example).
* `Script Preparation Code`: The JavaScript code that prepares the test environment and creates an object `obj` with multiple properties.
* `Html Preparation Code`: An optional HTML code that can be used to prepare the user interface for the benchmark (not provided in this example).

**Individual Test Cases**

There are two individual test cases:

1. **"for-in"`: This test case uses a traditional `for-in` loop to iterate over the properties of the `obj` object.
2. **"Object.keys"`: This test case uses the `Object.keys()` method to get an array of the object's property names, and then iterates over that array using a traditional `for` loop.

**Library: `Object.keys()`**

The `Object.keys()` method is a built-in JavaScript function that returns an array of strings containing all the enumerable properties found directly in an object. In this benchmark, it is used to get an array of property names from the `obj` object.

Pros:

* Efficient and concise way to iterate over object properties.
* Part of the ECMAScript standard, ensuring compatibility across browsers.

Cons:

* May not work as expected if the object has non-enumerable or inherited properties.
* May have a slightly higher overhead due to the creation of an array.

**"for-in"` Loop

The `for-in` loop is a traditional way to iterate over an object's properties. It is often used when working with legacy code or when the order of iteration matters.

Pros:

* Simple and easy to understand.
* Works with all types of objects, including non-enumerable and inherited properties.

Cons:

* Can be slower than using `Object.keys()` due to the overhead of iterating over the object's prototype chain.
* May not be as efficient for large objects.

**Other Alternatives**

In addition to these two approaches, there are other ways to iterate over an object's properties in JavaScript:

* Using a `for` loop with `in` operator: `for (var key in obj) { ... }`
* Using `Array.prototype.forEach()`: `obj.keys().forEach(function(key) { ... });`

However, these alternatives may not be suitable for this specific benchmark, as they would require additional modifications to the test code.

**Browser-Specific Considerations**

The benchmark results are provided for Chrome 89 on a Linux Desktop platform. This means that the performance differences between `for-in` and `Object.keys()` may vary across different browsers and platforms.

In general, it is essential to consider browser-specific quirks and limitations when writing JavaScript benchmarks to ensure accurate and fair comparisons.

Related benchmarks:

for in vs for loop with object.keys 123 (version: 0)

Comparing performance of: for-in vs Object.keys

Created: 5 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):