Defining the function using CFScript

function TotalInterest(principal, annualPercent,
   months) {

Starts the TotalInterest function definition. Requires three variables: the principal amount, the annual percentage rate, and the loan duration in months.

Var years = 0;
Var interestRate = 0;
Var totalInterest = 0;

Declares intermediate variables used in the function and initializes them to 0. All var statements must precede the rest of the function code.

principal = trim(principal);
principal = REReplace(principal,"[\$,]","","ALL");
annualPercent = 
   Replace(annualPercent,"%","","ALL");
interestRate = annualPercent / 100;
years = months / 12;

Removes any leading or trailing spaces from the principal argument. Removes any dollar sign ($) and comma (,) characters from the principal argument to get a numeric value.

Removes any percent (%) character from the annualPercent argument to get a numeric value, then divides the percentage value by 100 to get the interest rate.

Converts the loan from months to years.

   totalInterest = principal*(((1+ interestRate)^years)-1);
   Return DollarFormat(totalInterest);
}

Calculates the total amount of interest due. It is possible to calculate the value in the Return statement, but this example uses an intermediate totalInterest variable to make the code easier to read. Returns the result formatted as a US currency string.

Ends the function definition.