Javascript || not working

I'm Working on a banking application in which i have one drop-down box to select Mode of Payment and i have two text fields for Acc No and Bank Name.

I have three inputs for Mode of payment: 1.Bank Transfer,2.Cash and 3.DD/Cheque.Now I would like to display a pop up message If the user selects the Mode of payment as Bank Transfer or DD/Cheque and leaving the two text fields i.e.,Acc No and Bank Name as blank.

MY JavaScript:

if ($F('personnel_bank_detail_mode_of_payment') == 'Bank Transfer' || 'DD/Cheque') 
{
    if ($F('personnel_bank_detail_account_number') == '')
    {
        "* Please Enter Bank Account Number\n";
    }
    if ($F('personnel_bank_detail_bank_id') == '') 
    {
        "* Select Bank Name\n";
    }
}

The above code is working if the user selects Bank Transfer but it is not working for DD/Cheque. How Could i make my code to work for both.Any useful suggestions will be appreciated.

Thanks!

Solution

You need to repeat what you're comparing.

if ($F('personnel_bank_detail_mode_of_payment') == 'Bank Transfer' || $F('personnel_bank_detail_mode_of_payment') == 'DD/Cheque')

If you're having some trouble with this, you can make this more obvious to yourself in the future by using parentheses around every statement.

if ((something == otherthing) || (something == someotherthing))

For the behaviour you're expecting, both sides of the || need to be something that evaluate to a boolean, which the == operator returns.