jQuery.ajaxPrefilter() JQ Home  <<  Ajax  <<  jQuery.ajaxPrefilter()

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Type / Setting pre-filtering.

Description

The jQuery.ajaxPrefilter() Ajax method, allows us to filter custom Ajax settings or modify the existing settings, before sending each request and before they are processed by the $.ajax() method.

Shorthand version $.ajaxPrefilter()

• All subsequent Ajax requests using any function will use the new settings, unless overridden by the individual requests, until the next invocation of the $.ajax() method.

Syntax

Parameters

Return

undefined.

jQuery.ajaxPrefilter( [dataTypes], handler(settings, localSettings, jqXHR) ) ExamplesAjax  <<  Top

Filter custom Ajax settings or modify the existing settings, before sending each request and before they are processed by the $.ajax() method.

In the example below when we press the left button the first time, we create a custom setting using the jQuery.ajaxSetup() method. We then run the userRequest() function and within that create a deferred/promise to map to the output from a request. After this we call the jQuery.ajaxPrefilter() method and abort any request to the page not from a special user. We output a message confirming this.

In the example below when we press the right button the first time, we create a custom setting using the jQuery.ajaxSetup() method. We then run the userRequest() function and within that create a deferred/promise to map to the output from a request. After this we call the jQuery.ajaxPrefilter() method and accept the request to the page from a special user. We output a message confirming this, return the Promise of the jqXHR and then output messages accordingly.

$(function(){
  $('#btn7').one('click', function(){
    $.ajaxSetup({
      specialUser: false
    });
    checkUser();
  });
  $('#btn8').one('click', function(){
    $.ajaxSetup({
     specialUser: true
    });
    checkUser();
  });
  function checkUser() {
    returnedPromise = userRequest();
    /*
     * Here we can check our returned promise which we mapped
     * from our Ajax request and if done is a special user.
     */
    returnedPromise.done( function() {
      $('#div3').append('Special user! <br>>+++++++++++<br><br>');
    });
    returnedPromise.fail( function() {
      $('#div3').append('No special user! <br>>+++++++++++<br><br>');
    });
  }
  
  function userRequest() {
    var ourDeferred = new $.Deferred();
    var userPromise = ourDeferred.promise(); 

    $.ajaxPrefilter( function(settings, localSettings, jqXHR) {
      if(settings.specialUser) {
	    $('#div3').append('Special user setting exists! <br>');
      } else {
  	    $('#div3').append('No special user setting, abort! <br>');
  	    jqXHR.abort();  
      }
    });
    var jqxhr = $.ajax({
       type: "GET",
       url: "../../../js/get3.js",
       dataType: "script"
    });
    jqxhr.done(function(data, status, xhr) {
      $('#div3').append('Special user with prefilter, so resolve the deferred! <br>');
      ourDeferred.resolve();
    });
    jqxhr.fail(function(jqXHR, status, error) {
      $('#div3').append('Error with Ajax request! ' + status + ' ' + error + ' <br>');
      ourDeferred.reject();
    });
    // Return the jqXHR Promise object
    return userPromise;
  }
});

/*
 * The code for the external Javascript file called from 
 * $.ajax() (url: "../../../js/get3.js") is shown below.
 */
$(function(){
  var someText = 'Special users only. ';
  $('#div3').append('Message from get3.js: ' + someText + '
');
});

Related Tutorials

jQuery Advanced Tutorials - Lesson 8 - Ajax Low-Level Interface

• <<    jQuery.ajax()
• jQuery.ajaxSetup()     >>