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Java Script Auto update field within a form


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A form has 2 fields and a button. If a default date appears in field "A" then press update_button onclick action calls function that adds 7 days to the default date and result is returned to field "B". My JavaScript works great.


if I click the form field "A" (default date) a calendar will pop-up so that the default date can be changed. I change the default date then I click update_button onclick action calls function that adds 7 days to the newly selected date and result is returned to field "B". My JavaScript works great.



How can I have field "B" immediately updated when chages are made to field "A" without using an update button. Currently, my Update button calls the function with an onclick=upDate('dateOne', 'dateTwo')

Edited by gazdzid
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There's no ajax here, since the browser won't be talking to the server inbetween page requests. This can, and should be handled with pure javascript.


If you're not using a framework (pure javascript), you could use the onchange event rather than using the onClick event.


My preferred solution would be to use the jQuery UI datepicker; it allows you to easily specify a callback function when a date is selected. In this case, the callback function would figure out the new date and update field 'B' for you.


You can check out the Datepicker here.

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Hello monkeysaurus and team,


Thank you for your kind reply and the onchange suggestion. Some success was observed but need a little more assistance



1. I currently have within the tags for Field "A" I have onclick="ds_sh3(this) which is an original Calendar function. (calendar works)

2. I have added onchange="upDate('date3', 'date4') to add 7 days and returns result to field "B". (onhange doesnot trigger)


Note: Field "A" Calendar works however onchange was not triggered Field "B" remained blank.


Next Steps:

3. Removed onclick="ds_sh3(this) which is the calendar function

4. Manually changed date in field "A" onchange triggers Field "B" displays new date +7 days (cool)



onchange does become active if the change in a field is generated via function



Sorry to say that I am not familiar with jQuery UI but can I still use JavaSript fuction to select a date for Field "A" and have the fuction that adds 7 days automatically triggered by either using onchange, another type of tag controller, or automatically force a change? if so how? if not why? and most importantly thanks!!

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Feck, I'm in the same position, LW. It's been so long since I worked without jQuery, I'm not sure what's going on here.


I suspect, though I could be wrong, that you might be running into cross browser difficulties.


Do you have the page online anywhere where we could take a look at it?


Oh, and Flex? Are you having a giraffe?

Edited by monkeysaurus
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