How to force a program to wait until an HTTP request is finished in JavaScript?

Question

Hello,

Is there a way in JavaScript to send an HTTP request to an HTTP server and wait until the server responds with a reply? I want my program to wait until the server replies and not to execute any other command that is after this request. If the HTTP server is down I want the HTTP request to be repeated after a timeout until the server replies, and then the execution of the program can continue normally.

Any ideas?

Thank you in advance, Thanasis

Answer 1

You can perform a synchronous request. I only know how to do this with jQuery, though:

$(function() {
    $.ajax({
       async: false,
       // other parameters
    });
});

You should take a look at jQuery's AJAX API. I highly recommend using a framework like jQuery for this stuff. Manually doing cross-browser ajax is a real pain!

Answer 2

For this you can start loader in javascript as soon as page starts loading and then you can close it when request finishes or your dom is ready. What i am trying to say, as page load starts, start a loader . Then page can do multiple synchronous request using ajax , until and unless you didn't get response, do not close close loader. After receiving the desired in response in final call, you can close the loader.

Answer 3

You can use XMLHttpRequest object to send your request. once you send your request you can readyState property to identify state. readyState will have following different states.

uninitialized - Has not started loading yet loading - Is loading interactive - Has loaded enough and the user can interact with it complete - Fully loaded

ex:

xmlhttp.open("GET","somepage.xml",true);
xmlhttp.onreadystatechange = checkData;
xmlhttp.send(null);

function checkData()
{
    alert(xmlhttp.readyState);
}

hope this will help