Get maximum value of field in a list via javascript

[Lance Gurd]

Is there a way of getting the maximum value of a field in a list using javascript, the list is paginated, but I want the maximum value of all the possible records not just the 20 visible ones, using javascript so that I can act on the returned value and use it elsewhere on the dialog without having to do an AJAX callback (the way I am currently doing it)

[Davidk]

Re: Get maximum value of field in a list via javascript

I believe you've only got 20 data records (at least to start with) in the List. As you page through and request more, an Ajax Callback gets more data, but that's all you have to work with.

[Davidk]

Re: Get maximum value of field in a list via javascript

It's a bit silly... but you could try this...

SELECT CUSTOMER_ID, CustAmount, (SELECT  max(custamount)  AS maxamt FROM tblCustomers     ) AS maxamt 
FROM tblcustomers

This gives you the max value of a column... but it's included as a column on each row. It's the same number for every row.

However, Alpha is not really happy with this. Sometimes the builder reports that it can't parse the statement... although you can preview the statement.

I built the List with just Customer_Id and CustAmount first... tested it with Detail View updates... and then added the maxamt column in.

[CharlesParker]

Re: Get maximum value of field in a list via javascript

You might do better to create a view and build a separate list to display that in some way, perhaps you could have a button that displays the value you are looking for and have this list be the parent of another, etc. I would think about what your really after and the importance of it and what you would do with that knowledge AFTER you know it.

[Lance Gurd]

Re: Get maximum value of field in a list via javascript

Hi David and Charles,

I think I need to explain this a little better.

I have a dialog which has a parent list, which is categories, which is the parent to the items list. These are both based on the same mySQL table (items table). The items list is then parent to the prices list (item rates table) ( and the purchase orders list but that is irrelevant to my problem). The prices list is a list of rates from different suppliers (some items are supplied by up to 5 different suppliers and some suppliers give different rates for different end clients of ours), this are sorted by date order descending so that the newest rates are always near the top.

The items list has a detail view, so that new items can be entered, and the rates list has a detail view for entering new rates for an item.

At present the onSelect event of the items list fires an AJAX callback to get the highest price in the item rates table for an item and puts this into a textbox on the items detailview, then I have a calculated textbox that adds VAT to the highest price to give me a customer price.

What I want is to not use the callback in the onSelect event, but to use some javascript to find the highest price in the rates list (as the data is already there, a callback seems an unnecessary waste of resource) then set the textbox and customer price.

[Davidk]

Re: Get maximum value of field in a list via javascript

But didn't you say the rates list is paginated? If so, I don't think the data is there. I understand you don't want to make an additional call to the server to get the highest price... that was evident from your original post. That's why I posted a sample select that gives you the highest value on each row.

[Lance Gurd]

Re: Get maximum value of field in a list via javascript

Hi David

If I took off pagination on the rates list, is there a way in javascript?

[Davidk]

Re: Get maximum value of field in a list via javascript

Yes... I found this on StackOverflow... very nice. I knew you could get the max value in an array... but this gets you the max value in an array of objects.

var dataArray = {dialog.Object}.getListData('listCust');

var maxAmt = Math.max.apply(Math,dataArray.map(function(o){return o.CustAmount;}))

alert(maxAmt);

.getListData() gets you the data array of objects from a List Control.
CustAmount is the property of the object from which you want to get the max amount.

Amazing the stuff that's out there.

[Lance Gurd]

Re: Get maximum value of field in a list via javascript

Thank you David, I had found the math.max bit over the weekend, just couldn't work out getting the property of the array bit. Will try this now

[Lance Gurd]

Re: Get maximum value of field in a list via javascript

Just for everybody, this works brilliantly, is instant with no more slight delay while the callback returns a value that is already available. Thank you David