How to Sum Unique Values in an Array of Objects in JavaScript

Learn how to efficiently sum unique values in an array of objects based on a specific key using JavaScript. Get step-by-step guidance in this guide.
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How to Sum Unique Values in an Array of Objects in JavaScript

Working with arrays of objects can sometimes be tricky, especially when you need to perform operations like summing values while eliminating duplicates based on specific keys. In this guide, we will tackle the common problem of summing unique values in an array of objects using JavaScript.

The Challenge

Consider the following array of objects:

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You want to sum the value property of objects but only for unique keys. In this case, the desired output should yield a sum of 15 since there are three unique keys (pos, online, call), each contributing 5 to the total.

The Solution

To achieve this, we can break down the solution into the following steps:

Ensure Uniqueness: We will first create a unique representation of the objects based on the key property.

Sum the Values: Once we have a collection with unique keys, we can sum their corresponding values.

Step-by-Step Implementation

Here's how you can implement the solution in JavaScript:

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Breakdown of the Code

Reduce Function:

We use the reduce method to create an accumulator (c).

For each object (e) in the array, we check if the key (e.key) is already present in the accumulator. If it isn’t, we add the object to the accumulator. This effectively filters out duplicates based on the key.

Object.values:

After the reduction, we have an object that contains only unique keys. By using Object.values(), we can extract the values of this object into an array.

Mapping Values:

We then use map() to create a new array comprising the values of the unique keys (val.value).

Final Sum:

Finally, we sum these values using reduce() to get the total.

Conclusion

By following the above steps, you can efficiently sum unique values in an array of objects, giving you the desired output while avoiding duplicates. This approach is simple and effective, allowing you to manipulate data in JavaScript without unnecessary complexity.

Whether you're handling arrays in web development or backend processes, understanding how to deal with similar objects will greatly enhance your coding skills!