Add fahrenheit to celsius converter and test

src/index.js

@@ -8,10 +8,16 @@
 // Import the factorial function from the factorial.js file
 const { factorial } = require('./utils/factorial');
 
-// The main() function calculates the factorial of 5 and logs the result to the console
+const { convertToCelsius } = require('./utils/fahrenheit_to_celsius_converter');
+
+// The main() function calculates the factorial of 5 & converts the fahrenheit temp of 50 to celsius, and logs both results to the console
 async function main () {
   const result = factorial(5); // Call the factorial function with the value of 5
   console.log('factorial of 5 is', result); // Log the result to the console
+
+  const fahrenheitTemp = 50; // Fahrenheit temp to convert to Celsius
+  const celsiusTemp = convertToCelsius(fahrenheitTemp); // Convered temperature
+  console.log('the Celsius temperature is:', celsiusTemp); // log to console
 }
 
-main(); // Call the main function to calculate the factorial of 5
+main(); // Call the main function to calculate the factorial of 5 & convert the fahrenheit temp of 50

src/utils/fahrenheit_to_celsius_converter.js

@@ -0,0 +1,25 @@
+/**
+ * Author: Kaitlyn Kelly
+ * Date: 6/3/2026
+ * File: fahrenheit_to_celsius_converter.js
+ * Description: This script converts a fahrenheit temp to a celsius temp
+ */
+'use strict';
+
+// function to convert a fahrenheit temp to equal temp in celsius
+function convertToCelsius(n) {
+
+    // if n is not a number, throw error and return
+    if (typeof n !== 'number' || Number.isNaN(n)) {
+        throw new Error('Input must be a valid number');
+    }
+
+    // formula to convert n to a celsius temp & store in celsiusTemp variable
+    const celsiusTemp = (n - 32) * (5/9);
+
+    // round converted celsius temp to two decimal places & return value
+    return Math.round(celsiusTemp * 100) / 100;
+}
+
+// Export the function for use in other scripts
+module.exports = { convertToCelsius }; 

test/utils/fahrenheit_to_celsius_converter.spec.js

@@ -0,0 +1,30 @@
+/**
+ * Author: Kaitlyn Kelly
+ * Date: 6/3/2026
+ * File: fahrenheit_to_celsius_converter.spec.js
+ * Description: This script tests the convertToCelsius function
+ */
+'use strict';
+
+// import the convertToCelsius functon from its file
+const { convertToCelsius } = require ('../../src/utils/fahrenheit_to_celsius_converter');
+
+describe('fahrenheit_to_celsius_converter.js', () => {
+
+    // test that the function correctly converts a temperature to celsius
+    it('should convert a fahrenheit temperature to its celsius equivalent', () => {
+        const result = convertToCelsius(100);
+        expect(result).toBe(37.78);
+    });
+
+    // test that the function converts a negative number
+    it('should convert a negative temperature to its celsius equivalent', () => {
+        const result = convertToCelsius(-5);
+        expect(result).toBe(-20.56);
+    });
+
+    // test that the function throws an error when a non-number is supplied
+    it('should throw an error when a non-number is supplied as the input', () => {
+        expect(() => convertToCelsius("ten")).toThrow('Input must be a valid number');
+    });
+});