Overview of the Benchmark

The provided JSON represents a JavaScript benchmark that compares two approaches to iterate over an object's properties: for-in loop and using the Object.keys() method.

What is being tested?

In this benchmark, the following options are compared:

1. for-in loop: This is an older way of iterating over an object's properties in JavaScript. It uses a manual index (key) to access each property.
2. Object.keys() method: This is a built-in JavaScript method that returns an array of an object's own enumerable property names.

Pros and Cons

• for-in loop:

  • Pros: Can be used when the order of iteration matters or when you need to access both the key and value.
  • Cons: May iterate over inherited properties, which can lead to unexpected behavior. It also uses a manual index, which can be error-prone.

• Object.keys() method:

  • Pros: More concise and readable than the for-in loop. Does not include inherited properties in the result.
  • Cons: Requires an additional import for older browsers (prior to ECMAScript 2015). May have a slight performance overhead due to the creation of an array.

Library

None, as this benchmark uses only built-in JavaScript methods and does not rely on any external libraries.

Special JS Features/Syntax

• ECMAScript 2015+: The Object.keys() method was introduced in ECMAScript 2015 (ES6). This means that older browsers may not support it. To make this benchmark compatible with older browsers, you would need to add a polyfill or use a different approach.

Benchmark Preparation Code

The provided preparation code creates an object obj with 7 properties and assigns them integer values from 1 to 7.

Individual Test Cases

Two test cases are defined:

• Test Case 1: for-in loop: This test case uses a traditional for-in loop to iterate over the object's properties.
• Test Case 2: Object.keys() method: This test case uses the Object.keys() method to retrieve an array of property names, which is then iterated using a for...of loop.

Latest Benchmark Result

The benchmark was run on a Chrome browser with version 89.0.4389.82 on a Linux-based desktop device. The results are:

• for-in loop: Executed approximately 1.38 executions per second.
• Object.keys() method: Executed approximately 0.90 executions per second.

Note that the performance difference between these two approaches is relatively small, but Object.keys() may be slightly faster due to its optimized implementation.

Alternatives

Other alternatives for iterating over an object's properties include:

• Using a for...of loop with the spread operator (...) or Array.from().
• Using the for...in loop with the hasOwnProperty() method to exclude inherited properties.
• Using a library like Lodash, which provides a more robust and flexible way of working with objects.