Asynchronous Javascript - the light bulb moment! (runAction AJAX callback)

[mixter]

Today I fooled myself into thinking I could return a variable from an AJAX callback and access it further down the javascript function... NOT!

I will spare you the gory details, and have stripped out all the code except for the alert boxes and the runAction callback

essentially, in my case here, the javascript returned by the runAction callback executes last of all

So I wrote a long "note to self" and thought I would post it here as a "heads up" for the newbies amongst us, might saves someone a bit of time debugging if they stumble across this thread before hand...


I am calling this Javascript function in a UX dialog from the Client-Side Event: onInitializeComplete

function InitTimeSheet() {

alert('Begin InitTimeSheet'); 

//-----------------------------------------------------------
// ACTION JAVASCRIPT runAction

{dialog.object}.runAction('runSPtoCreateTimesheetRecordsUsingDaysheetID');

//
//NOTE: runAction runs asynchronously 
//it sends a message from the browser to the server, requesting XBasic code to execute on the server
//in the meantime, the javascript engine moves on, and the remainder of this function will process.
//This code will not wait for the call to the server to actually return javascript back to the browser
//(it's asynchronous!)
//so any javascript returned from this runAction will very likely execute last of all in the browser
//i.e. the code below the dotted line will execute first, before the javascript 
//is returned from the runAction callback 
//-----------------------------------------------------------

alert('End InitTimeSheet');    //note this alert will pop up before any javascript returned to the browser from the runAction above

} //End InitTimeSheet

My "light bulb moment" for how to handle asynchronous callbacks...

[Peter.Greulich]

Re: Asynchronous Javascript - the light bulb moment! (runAction AJAX callback)

Michael,

You can access a variable from an ajax callback in JS:

function xb as C (e as p)
   Dim vTest as C = "Alpha"
   xb = "var x = '" + vTest  + "'; alert(x);"
end function

Also, take a look at "this-then-that"

function jsSubmit() {
{dialog.object}.submit();
}

function jsRefresh() {
var po = {dialog.object}.getParentObject();
if(po) { 
po.refresh();
	}
}

function jsReset() {
{dialog.Object}.resetForm(false);
}

function jsClose() {
{dialog.Object}.closeContainerWindow(this);
}

A5.executeThisThenThat(jsSubmit,jsRefresh,jsReset,jsClose);

[Steve Workings]

Re: Asynchronous Javascript - the light bulb moment! (runAction AJAX callback)

See also the State variables. Very very powerful and way easy to use.

Video M58 from the A5 Control Panel video finder.

[mixter]

Re: Asynchronous Javascript - the light bulb moment! (runAction AJAX callback)

Thanks Steve, yes I use state variables, in fact the code I removed from the function above sets a state variable in the javascript which gets used in the XBasic callback.

They are very powerful, I can't really see why anyone would use session variables which expire, when we have state variables that can be passed around almost as easily, and persist with the page.

[mixter]

Re: Asynchronous Javascript - the light bulb moment! (runAction AJAX callback)

A5.executeThisThenThat(jsSubmit,jsRefresh,jsReset,jsClose);

Peter, that is exactly what I needed thanks!

I kind of knew that existed from the "run actions synchronously" radio button in the Javascript Actions editor

But I never knew how to use it in my code, thanks so much, I will definitely be using this!

This means I can now achieve what I first was trying to do, just returning a single variable from my callback to use in the remainder of the client side code, instead of how I was now starting to modify it... returning a huge chunk of javascript back from the callback instead of just one line.

[mixter]

Re: Asynchronous Javascript - the light bulb moment! (runAction AJAX callback)

You can access a variable from an ajax callback in JS:

Yes I already was, the problem was the rest of the javascript had already executed before I could make use of the returned variable

But now I can thanks to your great tip. executeThisThenThat!

[JPMPA]

Re: Asynchronous Javascript - the light bulb moment! (runAction AJAX callback)

Similar thread:
http://msgboard.alphasoftware.com/al...e-then-proceed

[mixter]

Re: Asynchronous Javascript - the light bulb moment! (runAction AJAX callback)

nice! a few more options presented.