Benchmark Overview

The provided benchmark is designed to compare the performance of two approaches in JavaScript: object spreading (obj spread) and creating a new Map from an existing object.

Object Spreading (obj spread)

In this approach, the let a = {...obj}; expression creates a shallow copy of the obj object by iterating over its entries and copying each property to a new object. This process involves:

1. Creating a new object {}.
2. Iterating over each key-value pair in obj.
3. Assigning the value of each pair (idx) to the corresponding key ('idx' + idx) on the new object.

Pros:

• Simple and intuitive syntax.
• Supports nested objects and arrays.
• Can be used when working with existing objects that have specific structure or content.

Cons:

• Inefficient for large datasets, as it involves creating a new object for each iteration.
• May lead to performance issues if the original object is deeply nested or contains many properties.
• May not handle some edge cases, such as objects with null or undefined values.

New Map (new Map)

In this approach, a new Map is created from an existing object using Object.entries(obj). This process involves:

1. Converting the object's entries to an array of key-value pairs.
2. Passing this array to the Map() constructor.

Pros:

• Efficient for large datasets, as it uses a data structure optimized for fast lookups and insertions.
• Handles nested objects and arrays correctly.
• Can be used when working with existing objects that have specific structure or content.

Cons:

• Requires JavaScript version 14 or later to use the Map() constructor.
• May require additional setup or configuration if using older versions of JavaScript.
• May not work as expected with some edge cases, such as null or undefined values.

Other Considerations

• When working with large datasets, creating a new Map may be more efficient than object spreading. However, this depends on the specific use case and requirements.
• In some cases, using Object.assign() instead of object spreading might be more suitable.
• The choice between object spreading and creating a new Map ultimately depends on the project's performance requirements, JavaScript version, and personal preference.

Benchmark Preparation Code

The script preparation code is as follows:

var data = new Array(100000).fill(undefined).map((_, i) => i)
var obj = data.reduce((obj, idx) => { obj['idx' + idx] = idx; return obj }, {})
var map = new Map(Object.entries(obj))

This code creates an array data with 100,000 elements, generates a reduced object obj using the provided script preparation code, and then creates a new Map map from obj.

Individual Test Cases

The benchmark consists of two test cases:

1. "Obj spread": This test case runs the expression let a = {...obj};.
2. "new Map": This test case runs the expression let a = new Map(map);.

These test cases are likely used to measure the performance differences between object spreading and creating a new Map for large datasets.

Latest Benchmark Result

The latest benchmark result shows that the "new Map" approach outperforms the "obj spread" approach. The results indicate that:

• The Chrome 103 browser with the Mac OS X 10.14.4 operating system achieves an average execution speed of 74.05840301513672 executions per second for the "new Map" test case.
• The same browser and operating system achieve an average execution speed of 16.384777069091797 executions per second for the "obj spread" test case.

This suggests that creating a new Map from an existing object is more efficient than using object spreading for large datasets in this specific benchmark scenario.