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Learn how to effectively isolate duplicates by a specific property in an array of JavaScript objects using a custom grouping function.
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How to Isolate Duplicates by Property from an Array of Objects in JavaScript

When dealing with arrays of objects in JavaScript, a common task is to find and isolate duplicates based on a given property. In this post, we will explore the process of grouping objects by a specified property—in this case, the id property. This can be particularly handy when you want to manage similar items in a collection, like categorizing fruits in our example.

Understanding the Problem

Let's consider an array of fruit objects where each object has an id and a name. Here's how our array looks:

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Your goal is to create multiple arrays containing the objects that have the same id. For example, you want results like this:

For id: 1:

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For id: 2:

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The Solution

To solve this problem, we can create two functions: one to group the objects by their id, and another to extract only the duplicates. Let's break down the steps needed to achieve this.

Step 1: Group By id Function

First, we need a function to group our objects based on the id property. Here’s a simple implementation:

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How It Works:

We initialize an empty object called group.

We loop through each element of the input array.

Using the id as a key, we initialize an empty array if it doesn't exist, and push the current element into it.

Step 2: Extract Duplicates Function

Once we have the grouped data, we can filter out the groups that contain fewer than two objects:

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How It Works:

We loop through the properties of the grouped object.

If any property (or group) has a length of less than 2, we remove it from the object.

Step 3: Putting it All Together

Now, let's put these functions together to process our original array:

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Final Output

After running this code, the final output will be an object that contains only the duplicates, structured as follows:

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Conclusion

Isolating duplicates by a property in an array of objects can be efficiently achieved with the methods we've outlined. By grouping the objects and then filtering out non-duplicates, you can easily manage collections of items based on specific characteristics. This technique can be invaluable for data manipulation in JavaScript applications.

Now you have the tools and knowledge to tackle similar challenges in your projects. Happy coding!