convertOctalToDecimal()

---

Step 1: Understanding the Problem

First, let's take a moment to understand what we're trying to accomplish. The goal is to write a JavaScript function that takes an octal (base 8) number as an input and converts that number into a decimal (base 10) number. This conversion is a common task in computer science and understanding how to do it could be useful in a variety of scenarios.

To start, let's create a function called convertOctalToDecimal that takes a single parameter, octalNumber.

function convertOctalToDecimal(octalNumber) {

}

---

Step 2: Initialize Variables

Inside our function, let's first initialize some variables. We’ll need a variable to hold the result of our conversion, and another to hold the length of our octal number.

Let’s initialize 'decimal' to 0 (this will store our result), and calculate the 'length' of our input number.

function convertOctalToDecimal(octalNumber) {
    let decimal = 0;
    let length = octalNumber.toString().length;
}

---

Step 3: Convert Octal to Decimal

Next, we're going to convert our octal number to a decimal number. To do this, we will reverse iterate over our octal number, converting each digit to decimal and adding it to our 'decimal' variable.

In this step, a key point to understand is that each digit in an octal number represents a power of 8. The right most digit represents 8 raised to the power 0, the next digit to the left represents 8 raised to the power of 1, and so forth.

So, we will use a loop to iterate through our number, on each iteration raising 8 to the power of the current index and multiplying by the current digit, and adding this to our 'decimal' variable.

function convertOctalToDecimal(octalNumber) {
    let decimal = 0;
    let length = octalNumber.toString().length;

    for(let i = 0; i < length; i++) {
        decimal += Math.pow(8, i) * Number(octalNumber.toString().charAt(length - i - 1));
    }
}

---

Step 4: Return Result

Now, we just return our 'decimal' variable from the function. This will give us our final result, the input octal number converted to decimal.

function convertOctalToDecimal(octalNumber) {
    let decimal = 0;
    let length = octalNumber.toString().length;

    for(let i = 0; i < length; i++) {
        decimal += Math.pow(8, i) * Number(octalNumber.toString().charAt(length - i - 1));
    }
    
    return decimal;
}

---

Conclusion

And that’s it! By writing this JavaScript function we learned how to convert an octal number to its decimal equivalent. This function could prove useful in various programming and computer science contexts. We followed steps such as initializing variables, iterating over the octal number, and returning the result, all while understanding the logic and mathematics of base conversions. Here is the final function in all its glory:

function convertOctalToDecimal(octalNumber) {
    let decimal = 0;
    let length = octalNumber.toString().length;

    for(let i = 0; i < length; i++) {
        decimal += Math.pow(8, i) * Number(octalNumber.toString().charAt(length - i - 1));
    }
    
    return decimal;
}

We can now use this function to convert any octal number to decimal!