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Thread: Javascript calculation multiple fields

  1. #1
    Join Date
    Jan 2013

    Javascript calculation multiple fields

    Hi there,

    I am creating a gym membership form - it will offer two different types of memberships at 3 different locations.

    All of these options could be housed in a drop down - or not.

    Once the user has selected their membership option I will need to add together a couple of lines of fees : so a start up fee + admin fee + (1week of cost+remaining number of days of cost in the week of purchase)

    The start up fee and admin fee are known costs $99 and $49. 1 week costs=$10.99. So the mathematical formula in the brackets would be ( if purchased on a sat) $10.99+(10.99*6)/7

    The form is a basic payment form other than these calculations.
    But any assistance would be greatly appreciated - I'm in the midst of learning javascript - but I'm just not able to tackle this type of calculation as yet.

  2. #2
    Join Date
    Nov 2002
    Flint, Michigan, USA
    If I understand correctly, would the equations be:


    If so, use the Date function to get the day number, subtract that from 7, and use the result as the multiplier in:


  3. #3
    Join Date
    Jan 2013
    function myDateFunction()
    var date = new Date();
    var today = date.getDay();
    var daily = 10.99/7;
    var days = [1, 7, 6, 5, 4, 3, 2];

    // select the tag with the the id Amount
    var x = document.getElementById('Amount');

    // insert the value into the input
    x.value = parseFloat(99 + 49 + (daily * days[today])+10.99).toFixed(2)


    I have this so far and it's working...
    But I need each of the amounts for : admin, start up and pro rata to be fed into their input fields on change - the change being the user's selection of this type of membership or another that doesn't have a start up fee ( so exactly the same but 0=start up fee)

    This next step has got me stuck!

    Many thanks for your help!

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