jquery $.post function call order

Question

In the following jquery function, can someone explain to me why "second" is being executed before "first"? I assume that the entire $.post request should be completed before the browser moves on to the next line of code, but that does not appear to be happening.

function getGUID () {
$.post(getGUIDScript, function(data, textStatus) { 
 alert("first");
 GUID = data;
 }, 
 'text');

 alert("second");  
}

Thanks for the responses below guys. For posterities sake, the code above can be written as is shown below to wait until the post is completed before moving on.

function getGUID () {
$.ajax({
type: "POST",
url: getGUIDScript,
async: false,
success: function(data) {
 alert("first");
 GUID = data;
}
});
    alert("second");
}

This will set off the first alert and then the second.

Answer 1

The post is done asynchronously so the following statement is executed before the first one completes. If you need them to be synchronous, you need to use $.ajax and set the async parameter to false. Better yet, use the callback mechanism for post to wait and perform the subsequent actions after the ajax call performed by the post is completed.

Answer 2

$.post() initializes an asynchronous POST request that takes a callback as an argument. The callback executes when the server returns a response to the POST request.

Answer 3

If you'd like to make a synchronous ajax call, you can set asyc to false. See http://docs.jquery.com/Ajax/jQuery.ajax#options