6 min read 

Your code appears to be a simple HTML page with embedded JavaScript that fetches and displays currency exchange rates using an external API. Here's a review of your code:

HTML Structure: Your HTML structure looks fine, but there are a few issues:

The <body> tag is not properly opened. You should have an opening <body> tag.
You have a <div> with class display-4, which seems to be a Bootstrap class. However, you haven't included Bootstrap's JavaScript and CSS files. Make sure to include them if you intend to use Bootstrap classes.
CSS Styling: Your CSS styling is good, but you could make it more organized by grouping related styles together. Also, avoid using inline styles when possible and rely on classes instead. Inline styles can make your code harder to maintain.

JavaScript:

The code structure looks reasonable, but there are some improvements that can be made:

The onLoad function is a self-invoking function. It would be more conventional to use the DOMContentLoaded event listener instead of a self-invoking function to ensure that the DOM is fully loaded before executing your JavaScript.
You have a function setButtonFunctions that is currently only setting the onclick event of the button. It's not necessary to have a separate function for this purpose. You can directly set the event handler when the page loads.
Avoid using hardcoded API keys in your code. In your case, you have an API key directly in the JavaScript. Consider storing sensitive information like API keys securely on the server and making requests to the server to fetch data.
API Request: Your API request code looks good. You're using the fetch API to make an asynchronous request to an external API, and you're handling the response appropriately.

Error Handling: You have error handling in place with .catch(err => {...}). This is good practice to handle potential errors when making API requests.

Code Organization: Consider organizing your code into functions or modules to make it more modular and maintainable, especially if you plan to add more functionality in the future.

Comments: Adding comments to explain the purpose of your functions and code blocks can be helpful, especially if others need to work with your code.

In summary, your code is functional for its current purpose, but there are some improvements you can make for better organization and maintainability. Additionally, consider addressing the issues related to the HTML structure and Bootstrap inclusion if you intend to use Bootstrap classes.