convertFahrenheitToCelsius()

Step 1: Understanding the problem

The first step in programming is to understand the problem statement and the requirements. In this case, we are tasked to create a function that converts degrees in Fahrenheit to degrees in Celsius. The formula for the Fahrenheit to Celsius conversion is (F - 32) * 5/9 = C, where F is the Fahrenheit temperature and C is the Celsius temperature. Now, let's move to the code implementation.

// This is just an empty function, we will fill it in the following steps
function convertFahrenheitToCelsius() {

}

Step 2: Adding parameters

Next, we will add the Fahrenheit degree as a parameter to our function. Parameters are values that the function will use when performing its task.

// Our function now takes a single argument: fahrenheitDegree
function convertFahrenheitToCelsius(fahrenheitDegree) {

}

Step 3: Implementing the conversion formula

Now that we have our function set up, the next step is to use the Fahrenheit to Celsius conversion formula in our code.

function convertFahrenheitToCelsius(fahrenheitDegree) {
  let celsiusDegree = (fahrenheitDegree - 32) * 5/9;
}

Step 4: Returning the result

Currently, our function correctly calculates the Celsius degree but doesn't do anything with it. So, we need to add one final line of code: a return statement. The return keyword is used to specify the result that a function should produce.

function convertFahrenheitToCelsius(fahrenheitDegree) {
  let celsiusDegree = (fahrenheitDegree - 32) * 5/9;
  return celsiusDegree;
}

Step 5: Testing our function

To make sure our function works correctly, it's a very good practice to test it by calling it with different inputs. Let's test it with 32°F (should return 0°C) and 212°F (should return 100°C).

console.log(convertFahrenheitToCelsius(32));  // 0
console.log(convertFahrenheitToCelsius(212)); // 100

Conclusion

That's it—we've just written a function in Javascript that converts degrees Fahrenheit to degrees Celsius! The full code is as follows:

function convertFahrenheitToCelsius(fahrenheitDegree) {
  let celsiusDegree = (fahrenheitDegree - 32) * 5/9;
  return celsiusDegree;
}

console.log(convertFahrenheitToCelsius(32));  // 0
console.log(convertFahrenheitToCelsius(212)); // 100

You can now use this function in your code whenever you need to perform this conversion. As you've seen, the process of writing a function involves understanding the problem, setting up the function and finally implementing the logic within the function. Happy coding!