How to Display Nearby Locations Using Radius in Your Google Maps React Application

Learn how to implement a Google Maps component in React that shows users nearby locations based on a certain radius, with tips on handling state management correctly.
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This video is based on the question https://stackoverflow.com/q/67562920/ asked by the user 'Bryson Sullivan' ( https://stackoverflow.com/u/15945797/ ) and on the answer https://stackoverflow.com/a/67563045/ provided by the user 'Matthew Kwong' ( https://stackoverflow.com/u/10579013/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Showing Users Nearby Locations Based on Radius

When developing applications that provide location-based services, it's often necessary to display nearby locations to users within a specific radius. This requirement is common for applications including delivery services, location finding apps, and even social networking tools that facilitate local events. If you're using React and Google Maps to accomplish this, it’s essential to ensure that your state is managed properly to display the expected results.

In this post, we'll walk through a common problem encountered when trying to implement such a feature and will provide a step-by-step solution to help you show users the nearest locations based on a radius they choose.

Problem Statement

Suppose you are building a Google Maps component that retrieves locations from a JSON file and later may utilize a database. The goal is to show users locations within a specific radius. However, while trying to set the state of the nearest locations, you notice that it only captures the last element in the array. This can be frustrating, especially when you correctly calculate distances but end up with incomplete data in your application.

Analyzing the Code

Here's the critical part of the code where the issue arises. In the handleSubmit function, you're using a loop to process the results and update the state:

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

Understanding the Issue

When using setNearestPlace() within this loop, you are continuously updating the state with the value of el. Since state updates in React are asynchronous, only the last value assigned to el will remain in the state after the loop execution. This means your nearestPlace will only contain the last entry of el.

Proposed Solution

Instead of trying to manage state within the loop, you should modify your approach to filter the results first and then set your state. Use the filter function to eliminate any undefined results before calling setNearestPlace. Here’s how:

Updated Code Snippet

Replace the existing forEach loop with the following:

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

Explanation of the Change

Filtering: The filter method is used to create a new array filled with elements that pass the test implemented by the provided function. In this case, we check if the elements are truthy (not null or undefined).

State Setting: After filtering the results, we set the state directly to this new array, ensuring that nearestPlace contains all valid entries.

Conclusion

By correctly managing your state, you have the ability to ensure that your Google Maps component effectively displays all locations within the user's specified radius. Utilizing the filter method not only resolves the issue of state management but also results in cleaner, more efficient code.

At the end of the day, testing is essential—make sure to check your applications thoroughly after implementing changes to ensure everything works as expected! Happy coding, and may your applications benefit from clear and helpful location data!