convertHexadecimalToOctal()

Step 1: Define the Function and Parse the Hexadecimal Input

First things first, we need to create our function and give it a parameter that will accept a hexadecimal number. Inside the function, we convert the hexadecimal number to a decimal number using JavaScript’s built-in parseInt function with 16 as the second argument, since hexadecimal is a base-16 number system. Here's the preliminary code:

function convertHexadecimalToOctal(hexNum){
    const decimal = parseInt(hexNum, 16);
}

Step 2: Convert to Octal

Now that we've converted our input to decimal, we still need to convert it to octal. javascript provides an easy way to do this using the toString method. Calling toString with 8 as the argument will convert our decimal number to base-8, i.e., octal.

function convertHexadecimalToOctal(hexNum){
    const decimal = parseInt(hexNum, 16);
    const octal = decimal.toString(8);
}

Step 3: Return the Result

Our function isn't very useful unless it gives us the octal number we're looking for. We can achieve this by simply adding a return statement, which will allow the calling code to access the converted number.

function convertHexadecimalToOctal(hexNum){
    const decimal = parseInt(hexNum, 16);
    const octal = decimal.toString(8);
    return octal;
}

Step 4: Test the Function

To make sure our function is working as we expect, we should test it with some known values. For example, if we pass the hexadecimal number "A2", the function should return "242", because A2 in hexadecimal is the same as 242 in octal. In a similar manner, you can test with other known values as per your need.

console.log(convertHexadecimalToOctal("A2"));  // expected output: "242"

Conclusion

That's it! We've just implemented a function that can convert a hexadecimal number to an octal number. Here's the full code again for reference:

function convertHexadecimalToOctal(hexNum){
    const decimal = parseInt(hexNum, 16);
    const octal = decimal.toString(8);
    return octal;
}

console.log(convertHexadecimalToOctal("A2"));  // expected output: "242"

Please bear in mind that there are many ways to accomplish this task. This is just one straightforward and efficient way to do it using JavaScript's built-in number conversion methods.