Benchmark Overview

The provided benchmark, hosted on MeasureThat.net, compares the performance of three approaches to iterate over the properties of an object:

1. for...in
2. Object.getOwnPropertyNames()
3. Object.keys() (with a custom filter)

Approach 1: for...in

The for...in loop iterates over the object's property names, including inherited ones. This approach is not recommended for performance-critical code because it can be slower due to the following reasons:

• It returns all properties, including non-enumerable ones (e.g., methods, event handlers).
• The iteration order may vary across browsers and environments.
• Some engines might use a slower algorithm for property iteration.

Pros:

• Simple and concise syntax.
• No additional dependencies required.

Cons:

• Potential performance impact due to the inclusion of non-enumerable properties.
• Unpredictable iteration order.

Approach 2: Object.getOwnPropertyNames()

This method returns an array containing all property names, including non-enumerable ones. The use of this approach is generally discouraged in modern JavaScript development due to its potential performance impact and less predictable behavior compared to other methods:

• Returns all properties, including non-enumerable ones.
• May be slower than other approaches.

Pros:

• Unambiguous result set (all property names).
• No filter needed for the loop.

Cons:

• Potential performance impact due to the inclusion of non-enumerable properties.
• Less predictable iteration order compared to for...in.

Approach 3: Object.keys() with custom filter

This approach uses Object.keys() to get an array of property names and then applies a custom filter to exclude properties starting with $. The use of this approach provides better performance due to the optimized filtering:

• Returns only enumerable property names.
• Provides control over which properties are included in the iteration.

Pros:

• Better performance compared to Object.getOwnPropertyNames().
• Easy to implement custom filtering logic.

Cons:

• Requires additional code for filter implementation.
• Might require browser support for newer JavaScript features (e.g., arrow functions).

Library Usage

In this benchmark, the obj object is defined using a template string, which includes special characters like $. The use of these characters in the benchmark suggests that MeasureThat.net supports running JavaScript tests with custom properties. The library used here is not explicitly mentioned, but it's likely that the test uses a subset of the ECMAScript standard.

Special JS Feature

The benchmark uses template literals (introduced in ECMAScript 2015) to define the obj object. This feature allows for more readable and efficient string concatenation. The use of template literals is generally considered best practice in modern JavaScript development.

Other Alternatives

If you need to compare these approaches, you could consider using a different testing framework or benchmarking tool, such as:

• Benchmark.js
• js-perf
• Benchmark

These tools provide more advanced features and customization options for writing and running benchmarks.