Convert Numbers to Roman Numerals

Convert Numbers to Roman Numerals

Table of Contents

1. Introduction
2. Creating the HTML Structure
3. Styling the Converter with CSS
4. Adding Functionality with JavaScript
5. Testing the Converter
6. Conclusion

Introduction

In this tutorial, we will learn how to create a number to Roman numeral converter. This converter allows users to enter a number and converts it into its equivalent Roman numeral representation. We will create the HTML structure, style the converter with CSS, add functionality with JavaScript, and test the converter to ensure it works correctly.

Creating the HTML Structure

To start, let's create the HTML structure for our converter. We will use a div element with the class "container" as the main container for the converter. Inside the container, we will have a div element with the class "input-wrapper" to hold the input field and the convert button side by side. The input field will be an input element with the type set to "number" and the ID set to "input". We will also add a placeholder text to provide a hint to the user. Next, we will add a button element with the ID "submit" to trigger the conversion process. We will display the converted Roman numeral in a paragraph element with the ID "output" and any error messages in a separate paragraph element with the ID "error".

Styling the Converter with CSS

Now that we have created the HTML structure, let's style the converter using CSS. We will start with some common styles using the universal selector, setting padding and margin to 0 for all elements and using the border-box sizing model. Then, we will target the body element to set its background color to a vibrant shade of blue. Moving on, we will style the container class to give the main container a white background color and set its width to be responsive. We will use the "min" function to calculate the width at 90% of the viewport width or a maximum of 450 pixels. The container will be positioned absolutely at 50% from the top and left, ensuring it is centered horizontally and vertically on the page. We will also add some padding and a border radius to give the container a visually pleasing look. Inside the container, we will style the input-wrapper class to create a grid layout for the input field and the convert button. We will use the display grid property and set the grid template columns to divide the available space into a 9:3 ratio with a gap of 1em between the columns. We will then style the input element, adding padding and setting the text color to dark gray. We will apply a border of 2px solid light gray and change the border color to blue when the input is focused, giving a visual indication to the user. Moving on, we will style the button element, giving it a background color of blue, a text color of white, and removing the border.

Adding Functionality with JavaScript

With the HTML and CSS in place, let's add functionality to our converter using JavaScript. We will start by declaring four variables: input, button, error, and output. We will assign them the corresponding elements from the HTML using the getElementById method. These variables will allow us to interact with and manipulate the elements on our web page. Next, we will define a constant variable called "Roman" object. This object will serve as the base for our Roman numeral conversion. It will contain key-value pairs where each key represents a Roman numeral and its corresponding value represents the equivalent decimal value. This object will provide us with the necessary conversion information. Moving on, we will use the addEventListener method to attach a click event listener to the button element. This means that when the button is clicked, the function specified inside the event listener will be executed. In this case, we will call the "inputToRoman" function and pass the value of the input element as an argument. We will also clear the value of the input field by assigning it an empty string, ensuring it is ready for the next number. Let's examine the "inputToRoman" function. This function takes a "num" parameter, which represents the input number from the user. Inside the function, we will first convert the input number to an integer using the parseInt method. This ensures that we are working with a valid number for the conversion. We will then check if the trimmed length of the input, after removing any leading or trailing white spaces, is 0. If it is, we will display an error message by setting the innerHTML of the error message element to "Invalid input". We will also return false to end the function's execution in this case. Next, we will check if the input number is greater than 4999 or less than 1. If it is, we will display another message stating that the input is out of range. Again, we will set the innerHTML of the error message element accordingly and return false. Now, let's initialize the "result" variable to store the converted Roman numeral. We will iterate over the keys of the Roman object using the Object.keys method and a for...of loop. For each key, we will compare the Roman numeral's decimal value with the remaining number and append the corresponding Roman numeral to the result string while decrementing the number accordingly. Finally, we will set the innerHTML of the output element to the result, displaying the converted Roman numeral to the user. To ensure the previous output is cleared, we will set the innerHTML of the output element to an empty string in both if conditions of the error message handling.

Testing the Converter

Now that we have created the HTML structure, styled the converter with CSS, and added functionality with JavaScript, let's test the converter to ensure it works correctly. Enter a valid number in the input field and click the convert button. The converted Roman numeral should be displayed in the output paragraph. If you enter an invalid number or encounter an error, an error message should be displayed in the error paragraph. You can continue testing the converter with different input numbers to ensure it handles all scenarios correctly.

Conclusion

In this tutorial, we have learned how to create a number to Roman numeral converter using HTML, CSS, and JavaScript. We have created the HTML structure, styled the converter with CSS, added functionality with JavaScript, and tested the converter to ensure it works correctly. By following the steps outlined in this tutorial, you can create your own number to Roman numeral converter and enhance your web development skills.