How to Convert jQuery $getJSON Call to Vanilla JS Using Fetch API

Learn how to seamlessly transition from jQuery's `$getJSON` to a more modern approach using the `Fetch API` for real-time currency conversion.
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Transitioning from jQuery to Vanilla JavaScript with Fetch API

In the world of web development, keeping your projects up to date with the latest technologies is essential. One common task you might encounter is fetching data from an API, like the Open Currency Exchange API for real-time currency conversion. Many developers have used jQuery’s $getJSON for this purpose, but what happens when you want to convert your code to vanilla JavaScript using the Fetch API? Here, we break down how to make that transition effectively.

The Problem: Code Functionality

Your challenge arises when the conversion logic fails due to the way JavaScript manages asynchronous operations and variable scope, specifically when accessing the fx object in the callback.

The Solution: Understanding Fetch and Callbacks

When utilizing the Fetch API, it's essential to manage your callbacks properly to ensure the expected JavaScript objects are returned at each step of your .then calls. Here’s a simplified structure to guide you through the transition:

Step 1: Fetch the Data Correctly

Your first then should be receiving the parsed JSON data and returning it adequately to be used in the next step. You were previously logging the data, which resulted in each successive then receiving undefined. Here’s how to properly structure it:

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

Step 2: Ensure Proper Variable Access

The main issue arises if the preceding .then does not return the necessary object. By returning the data from the second .then, you ensure that the next callback has what it needs to execute correctly. Here's the segment of code that highlights this:

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

Step 3: The Conversion Logic

Finally, your conversion logic can remain much the same. Just ensure that you access data correctly:

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

Conclusion

Transitioning from jQuery's $getJSON to vanilla JavaScript using the Fetch API is a manageable task that brings your project up to modern standards. Always remember to return values correctly in your promise chains to facilitate seamless data flow between your callback functions. With this approach, you'll be on your way to creating a more efficient and updated JavaScript application.

Keeping your APIs and libraries up to date not only improves performance but also broadens the compatibility with newer web standards. Happy coding!