Fluctuating between different currencies

I have been trying to tackle this issue for some time now - how can I set up the functionality to switch between currencies seamlessly? The first select dropdown should include options for EUR, USD, and GBP, while the second should offer UAH, GBP, and EUR. However, once a currency is selected in the first dropdown, it should be removed from the options in the second dropdown and vice versa. How can I achieve this dynamic behavior?

const [selectOne, selectTwo] = document.querySelectorAll('.custom-select');
// More JavaScript code here
// CSS styling here
<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <title>Currency Converter</title>
    <link rel="shortcut icon" href="currencies-icon-10.jpg" type="image/x-icon">
    <link rel="stylesheet" href="style.css" />
  </head>
  <body>
    <div class="container">
      // HTML structure here
    </div>
    <script src="script.js"></script>
  </body>
</html>

Answer №1

I made minimal changes to the HTML and CSS styling, with a few exceptions like adding ids to the currency dropdowns for easier element fetching and setting the second amount as read-only for a better user experience.

The JavaScript code was refactored for improved readability. I may have altered some parts of your code to enhance functionality, such as saving state in the DOM to encapsulate functions better and avoid reliance on external variables.

This demonstration showcases a functional currency converter where the dropdown menus are initialized without overlapping, ensuring that when one currency is changed, the corresponding option in the other dropdown disappears. The currency rates displayed on the labels and the second amount are updated upon changing currencies or entering a new value in the first amount field.

By triggering the swap function, the positions of the currencies are switched, updating the entire interface accordingly.

Note: Repeatedly swapping currencies can lead to small discrepancies due to floating-point number usage in JavaScript, which can result in accumulating offsets with each swap operation.

To illustrate this issue, consider the following scenario:

[USD=>EUR] [exchange rate E/$: 0.9783] [102$ * 0.9783 = 99.7866] [approx: 99.79E]

As you continue swapping and recalculating, the rounded values will deviate further from the original input, demonstrating the limitations of using floating-point numbers for currency operations in JavaScript.

Despite these challenges, the added functionality maintains the core architecture of the original code while enhancing its usability. Detailed comments have been provided to aid in understanding the modifications applied.

// Updated JS functions
function initializeAmount(){  
  // Function logic here
}

function initializeSwap(){
  // Function logic here
}

// More Functions and Logic

}, { styles omitted for brevity }

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