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Discover how to efficiently sum values in a JSON array grouped by `shop_id` using Lodash and JavaScript. Learn step-by-step in this informative guide!
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This video is based on the question https://stackoverflow.com/q/67299363/ asked by the user 'Özenç B.' ( https://stackoverflow.com/u/8131366/ ) and on the answer https://stackoverflow.com/a/67299989/ provided by the user 'Bronislav Růžička' ( https://stackoverflow.com/u/12695343/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Aggregate Values in JSON Objects with Lodash

In the realm of JavaScript, manipulating JSON data is a common task, especially when it comes from APIs or databases. A frequent requirement is to aggregate values from this data without specifying explicit keys. In this guide, we will tackle a specific problem: how to sum values in a JSON array grouped by shop_id using Lodash.

The Problem

Input Data Structure

Consider the following JavaScript array:

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

In this array, each object represents sales data associated with a shop_id. Your goal is to aggregate these sales amounts by shop_id so that the resulting output looks like this:

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

The Solution

To achieve this, you can leverage the power of JavaScript's reduce() function alongside some simple object manipulations. While Lodash can make these tasks easier, it's also possible just with plain JavaScript. Let's break down the steps to implement this solution.

Step-by-Step Breakdown

Initialize an Empty Accumulator

You’ll start by creating an empty object to hold the aggregated sales data indexed by shop_id.

Loop Through the Array

Use the reduce() method to loop through the input array and build your accumulator.

Merging Objects

For each element in the array, check if the shop_id already exists in the accumulator. If it does, merge the sales from the current object into the existing object. If not, create a new entry in the accumulator.

Extract Values

The final step is to convert the accumulated object back into an array using Object.values().

Implementing the Code

Here's the complete code you would use:

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

Explanation of Key Parts

Accumulator Function:

This custom function checks if shop_id already exists. If yes, it merges the sales values. If not, a new entry is created.

Object.entries():

This method is crucial for iterating over the sales keys so that you can sum the values accordingly.

Deep Copy:

When creating a new entry, use the spread operator { ...value.sales } to ensure you create a fresh object rather than referencing the original.

Conclusion

By following these steps, you can efficiently aggregate values in a JSON array grouped by a specific key using JavaScript. This method is efficient and avoids the need for backend database operations for simple aggregations. So next time you need to work with sales data or similar JSON structures, consider using this approach!

Now that you have the solution, go ahead and implement it in your project, and enjoy the benefits of cleaner, more efficient code!