ajax rount-trip in javascript if/else statement

[pbd22]

can somebody tell me how i can use an ajax call in a
javascript if/else statement that only goes to the next
else statement after the ajax round-trip returns a true/false
result? code appreciated.

thanks!

 

[Thomas 'PointedEars' Lahn]

can somebody tell me how i can use an ajax call in a
javascript if/else statement that only goes to the next
else statement after the ajax round-trip returns a true/false
result?

1. You can't.
2. Make the request-response handling synchronous (not recommended).

code appreciated.

You mistyped "doing your homework" only slightly.



PointedEars

 

[pbd22]

so how do you make an xmlhttp request part of a
conditional code block without making the call synchronous?

 

[Hamish Campbell]

how i can use an ajax call in a javascript

You mistyped "doing your homework" only slightly.

Yep, homework question number 1: "What does the first A in AJAX stand
for?"

 

[Hamish Campbell]

so how do you make an xmlhttp request part of a
conditional code block without making the call synchronous?

You don't, you use the readystatechange event to call a function when
a response is received.

 

[Thomas 'PointedEars' Lahn]

Yep, homework question number 1: "What does the first A in AJAX stand
for?"

You destroyed the context of my comment, though. Learn to quote.

<http://jibbering.com/faq/#posting> pp.


PointedEars

 

[Hamish Campbell]

That's interesting.  I never thought about that before -- that AJAX was

an acronym.  So why, then, is it still possible to make an AJAX call
synchronous?  It sounds like that would be an oxymoron.

What you do with the *xmlhttp* object is entirely up to you. Calling
it AJAX doesn't make it so.

 

[Richard Cornford]

Fair enough. Since it is the same structure and process,
maybe we should call that SyJAX ?

Maybe we should take the point that synchronous XML HTTP requests are
such a seriously bad idea that there is no need for inventing a name
for them, as they wouldn't be being used.

Richard.

 

[Gregor Kofler]

sheldonlg meinte:

That's interesting. I never thought about that before -- that AJAX was
an acronym. So why, then, is it still possible to make an AJAX call
synchronous? It sounds like that would be an oxymoron.

You don't even need XML with AJAX.

Gregor

 

[pbd22]

You don't, you use the readystatechange event to call a function when
a response is received.

I understand how an xmlhttp request/response works, but I am having
problem with the following (pseudocode):

if (condition) { //do something
}else if (condition) { // use xmlhttp to get a result of some sort.
{ else { // do something }

The problem with the above is that the code does not wait for the
round-trip xmlhttp response. It hits the else statement that fires the
request, considers its work done, and moves on. I understand that this
is caused by the "A" in AJAX but, if i have to get a result from the
server to satisfy a condition in a JavaScript code block, how might I
otherwise go about it (that is not "SynJax")?

Thanks.

 

[Matthias Reuter]

I understand how an xmlhttp request/response works, but I am having
problem with the following (pseudocode):

if (condition) { //do something
}else if (condition) { // use xmlhttp to get a result of some sort.
{ else { // do something }

The problem with the above is that the code does not wait for the
round-trip xmlhttp response. It hits the else statement that fires the
request, considers its work done, and moves on. I understand that this
is caused by the "A" in AJAX but, if i have to get a result from the
server to satisfy a condition in a JavaScript code block, how might I
otherwise go about it (that is not "SynJax")?

Well, you have to start using callbacks.

if (condition) {
doSomething();
}
else if (condition2) {
doHttpRequest(doSomething2);
}
else {
doSomething3();
}

with functions doSomething, doSomething2 and doSomething3.

Example:

if (emailAddress) {
sendMail(emailAddress);
}
else {
loadAddress();
}

function loadAddress () {
// ... get xmlhttprequest

r.onreadystatechange = function () {
emailAddress = r.responseText;
sendEmail(emailAddress);
};

// ... send request
}