Filtering and Reducing an Array of Objects by Day in JavaScript

Learn how to filter and reduce an array of objects in JavaScript based on unique days while calculating average values using ES6 methods.
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Filter and Reduce an Array of Objects by Day in JavaScript

In web development, managing and manipulating data efficiently is essential. One common scenario developers face is filtering and reducing arrays of objects to extract meaningful information. For instance, if we're working with an array that records daily readings, we might want to filter this data based on the day and calculate average values for each day. In this guide, we will explore how to achieve this in JavaScript using ES6 array methods, particularly the filter and reduce functions.

The Problem: Filtering Data by Day

Imagine we have the following array of objects called data, which contains records of readings, including their severity levels and timestamps:

[[See Video to Reveal this Text or Code Snippet]]

From this data, we want to create an object that summarizes the severity levels by day, noting each day's average severity. Our goal is to achieve output like this:

[[See Video to Reveal this Text or Code Snippet]]

The Solution: Step-by-Step Approach

To filter and reduce the array into a new object based on the unique days in the dataset, we can follow these steps:

Step 1: Get a Unique List of Days

First, we need to extract unique dates from the data array. We can do this using the Set object in JavaScript combined with the map method:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Build an Object Based on These Unique Days

Next, we'll create an object where each key is the unixDate for a specific day, and the value is the average severity level. We can achieve this by using the map and filter methods:

[[See Video to Reveal this Text or Code Snippet]]

Full Code Implementation

Putting it all together, the complete code looks like this:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By following these steps, we not only filtered our array of objects based on unique days but also calculated the average severity level for each day. This solution demonstrates the power of ES6 array methods such as map, filter, and reduce, which can simplify complex data manipulations.

If you're dealing with similar data structures in your applications, remember that understanding these methods can greatly improve your efficiency in handling and presenting data. Happy coding!