$.ajaxPrefilter() Vs $.ajaxSetup() - jQuery Ajax

Question

While learning through ajax in jQuery, I came across 2 terms, viz., $.ajaxPrefilter() and $.ajaxSetup(). All I can find out is that these make some changes in AJAX before loading or making call to $.ajax().

Can someone simplify and explain these terms in easiest form along with a slight comparison of the two?

Answer 1

$.ajaxSetup() - Set default values for future Ajax requests. You could, for example, set the ajax URL that you always want to use for every request here.

Example:

$.ajaxSetup({
  // Always use this URL for every request
  url: "http://example.com/ajax.php"
});

---

$.ajaxPrefilter() - Modify existing options before each request is sent. You could, for example, append a query string component to every ajax request that is sent out.

Example:

$.ajaxPrefilter( function(options) {
    // Always add "?debug=1" to every URL
    options.url += (options.url.indexOf("?") < 0 ? : "?" : "&") + "debug=1";
});

Answer 2

$.ajaxSetup simply takes an options object, and uses it as the defaults for future $.ajax() calls (and other calls that are shortcuts for this, like $.get). For instance,

$.ajaxSetup( { dataType: 'json' });

makes this the default dataType for future calls.

$.ajaxPrefilter lets you run a custom function before sending each AJAX request to the server. It can examine the options to that call, and then change them in any way that it wants. So it provides much more flexibility and control than $.ajaxSetup.