How to Return Unique Objects from an Array in Javascript

Learn how to return unique objects from an array in Javascript and create dynamic dropdown menus to enhance user experience.
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Return Unique Objects from an Array in Javascript

When working with arrays that contain complex objects in Javascript, you may encounter situations where you need to extract unique entries based on certain properties. In this guide, we’ll tackle the problem of returning unique objects from an array while providing meaningful context, especially useful for populating dropdown menus in web applications.

The Problem

Consider the following array of objects in Javascript:

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You need to create two dropdown menus:

The first dropdown should list the unique id values: A and B.

The second dropdown should dynamically show the corresponding version based on the selection made in the first dropdown.

While it’s simple to extract unique ids using a Set as shown below, it doesn't retain the additional properties needed for the second dropdown:

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This results in a loss of context since we're only getting the id values. Instead, you want to maintain the entire object format as follows:

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The Solution

To achieve the desired outcome, we can group the objects based on their id and then populate the second dropdown based on the selection from the first. Below is a step-by-step breakdown of the solution:

Step 1: Grouping the Data

First, we group the data by id, which will allow us to retrieve the necessary information for the dropdowns later on. We can use the reduce method:

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Step 2: Creating HTML Elements

Next, we need to create the dropdowns programmatically using the HTML DOM:

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Step 3: Populating the First Dropdown

Now, we can populate the first dropdown with the unique id options:

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Step 4: Setting Up the Second Dropdown

To populate the second dropdown based on the selected id, we create a function called setOptions:

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Initially, call setOptions with a default value (e.g., 'A'):

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Step 5: Handling Dropdown Changes

Finally, we handle changes to the first dropdown, so that selecting a new id dynamically updates the second dropdown:

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Final Code

Below is the complete code for creating dynamic dropdowns based on unique objects:

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

Conclusion

By following these steps, you can efficiently extract unique objects from an array and create a user-friendly interface with two dropdown menus. This approach not only enhances user experience but also demonstrates the power and flexibility of Javascript when handling complex data structures.

With these techniques at your disposal, you can create dynamic forms that react to user input with minimal delay, making your web applications feel more interactive and responsive.

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