没有回调成功功能的嵌套AJAX请求

Question

After reading this thread jQuery Ajax Request inside Ajax Request

Hi everyone I need to have explanations about such a situation. I've just been working on the code of a former member of my development team and found many parts of the code where he makes asynchronous ajax calls within other ajax calls.

My question is : can anyone explain the advantages and disadvantages of this practice and whether it is a good or bad practice?

Here is an example of code:

// first ajax (starting ajax call)
$.ajax({
    url: "script1.php", 
    type: "POST", 
    data: {paramFisrtAjax: "first-ajax"},
    success: function(response) {
       alert(response);
    }
});

script1.php

<script>    
// second ajax
$.ajax({
    url: "script2.php", 
    type: "POST", 
    data: {paramFirstAjax: "<?= $_POST['paramFisrtAjax'] ?>", paramSecondAjax: "second-ajax"},
    success: function(response) {
        alert(response);
    }
});
</script>
<?php 
// some operations on database server
echo "page2 operations with param: paramFirstAjax-> {$_POST['paramFirstAjax']}"; 
?>

script2.php

<?php 
// some operations on database server
echo "page3 operations with params: firstParam -> {$_POST['paramFisrtAjax']} and secondParam-> {$_POST['paramSecondAjax']}";
?>

Something tells me it's not a good thing becouse i think the correct way is use the callback function success . Like this: jquery nested ajax calls formatting

Answer 1

There is an advantage and a disadvantage here.

The Advantages are:

1) You make an async call, making the request a lot faster . You do not wait for the callback function, thus do not wait for your response which might take time to return . You do everything on the background rather then 'straight forward'. This is understandable when you call multiple methods and you do not want the delay in waiting for the callback.

2) You are able to fetch a far greater amount data through your call while minimizing the need of the end client to wait. This is useful when you have a big amount of data to display and you want to make it with minimal effort.

The Disadvantages:

1) Error handling is a pain. I f something fails within the inner calls, it takes time to detect were the failure occurred and on which method . When waiting for the callback, you can detect right away where the error occurred, as it will return a response of success or error,

2) if there is a mismatch on the data, it is hard to track back and see where the missing part took place, you will have to go through each request one by one to detect and use developer tools and/or fiddler as well , since those are async calls at the end.

3) it is easy to put too much effort on the client, since maintaining this kind of technique might result in calling multiple methods that will work together at the same time, thus creating overload on the client, locks on the threads or DB when working with server side code and more.

This explained, you can now decide for yourself with which type of method you would like to continue further in your code.