Скачать или смотреть How to Loop and Group Values by Checking Keys in an Array of Objects Using JavaScript

Learn how to handle arrays of objects in JavaScript by looping through them and grouping values based on the presence of keys.
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This video is based on the question https://stackoverflow.com/q/77831529/ asked by the user 'Vikas Acharya' ( https://stackoverflow.com/u/8750174/ ) and on the answer https://stackoverflow.com/a/77831604/ provided by the user 'Amit Mohanty' ( https://stackoverflow.com/u/2285394/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Loop and Group Values by Checking Keys in an Array of Objects Using JavaScript

When working with data in JavaScript, it's common to handle arrays of objects. Sometimes, we need to process this data based on certain conditions, such as whether specific keys are present or not. In this guide, we will explore how to solve a problem that involves combining values based on the presence of the keys time and endTime in an array of objects.

The Problem

You have an array of objects structured like this:

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

The goal is to create a new array that includes:

Values from the time key at odd indices.

The endTime value if the last result array's length is odd.

Both values (time and endTime) if the last result's length is even.

Expected Output

The desired output from processing this array is as follows:

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

Breaking Down the Solution

Let’s walk through how to implement this using JavaScript’s reduce() function. The reduce method is perfect for this scenario, as it allows us to iterate through the array and build a new array based on specific conditions.

Step-by-Step Implementation

Initialize the Array and Reduce Function:

We'll start with the following setup:

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

Here, pv represents the accumulator (prev value), and cv is the current object being processed.

Checking for endTime:

Next, check if the endTime key exists in the current object (cv).

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

This code pushes the time value to the result array res if endTime is not present.

Handling Both time and endTime:

If the endTime key exists, we need to determine if the result array's length is odd or even:

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

If the length of the result array is odd, we push only endTime.

If the length is even, we push both time and endTime.

Returning the Result:

Finally, we return the accumulated result:

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

Complete Code

Here is the complete code for clarity:

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

Conclusion

In this post, we tackled the challenge of looping through an array of objects in JavaScript and grouping values based on the presence of keys. The use of reduce() provides an elegant solution while keeping the code clean and readable. We hope this explanation helps you in your JavaScript programming journey!

Happy coding!