JAVASCRIPT

make ajax calls with jQuery

// GET Request
    $.ajax({
        url: "example.php?firstParam=Hello&secondParam=World", //you can also pass get parameters
        dataType: 'json',	//dataType you expect in the response from the server
        timeout: 2000
    }).done(function (data, textStatus, jqXHR) {
        //your code here
    }).fail(function (jqXHR, textStatus, errorThrown) {
        console.log("jqXHR:" + jqXHR);
        console.log("TestStatus: " + textStatus);
        console.log("ErrorThrown: " + errorThrown);
    });

//POST Request
    var formData = {name: "John", surname: "Doe", age: "31"}; //Array 
    $.ajax({
        url: "example.php",
        type: "POST", // data type (can be get, post, put, delete)
        data: formData, // data in json format
       	timeout: 2000,	//Is useful ONLY if async=true. If async=false it is useless
        async: false, // enable or disable async (optional, but suggested as false if you need to populate data afterwards)
        success: function (data, textStatus, jqXHR) {
            //your code here
        },
        error: function (jqXHR, textStatus, errorThrown) {
            console.log("jqXHR:" + jqXHR);
            console.log("TestStatus: " + textStatus);
            console.log("ErrorThrown: " + errorThrown);
        }
    });


//Alternatively, the old aproach is
    $.ajax({
        url: "api.php?action=getCategories",
        dataType: 'json',
        timeout: 2000,
        success: function (result, textStatus, jqXHR) {   //jqXHR = jQuery XMLHttpRequest
            /*You could put your code here but this way of doing it is obsolete. Better to use .done()*/
        },
        error: function (jqXHR, textStatus, errorThrown) {
            console.log("jqXHR:" + jqXHR);
            console.log("TestStatus: " + textStatus);
            console.log("ErrorThrown: " + errorThrown);
        }
    });

jQuery AJAX methods

$.ajax()			Performs an async AJAX request
$.ajaxPrefilter()	Handle custom Ajax options or modify existing options before each request is sent and before they are processed by $.ajax()
$.ajaxSetup()		Sets the default values for future AJAX requests
$.ajaxTransport()	Creates an object that handles the actual transmission of Ajax data
$.get()				Loads data from a server using an AJAX HTTP GET request
$.getJSON()			Loads JSON-encoded data from a server using a HTTP GET request
$.parseJSON()		Deprecated in version 3.0, use JSON.parse() instead. Takes a well-formed JSON string and returns the resulting JavaScript value
$.getScript()		Loads (and executes) a JavaScript from a server using an AJAX HTTP GET request
$.param()			Creates a serialized representation of an array or object (can be used as URL query string for AJAX requests)
$.post()			Loads data from a server using an AJAX HTTP POST request
ajaxComplete()		Specifies a function to run when the AJAX request completes
ajaxError()			Specifies a function to run when the AJAX request completes with an error
ajaxSend()			Specifies a function to run before the AJAX request is sent
ajaxStart()			Specifies a function to run when the first AJAX request begins
ajaxStop()			Specifies a function to run when all AJAX requests have completed
ajaxSuccess()		Specifies a function to run when an AJAX request completes successfully
load()				Loads data from a server and puts the returned data into the selected element
serialize()			Encodes a set of form elements as a string for submission
serializeArray()	Encodes a set of form elements as an array of names and values

jQuery AJAX Methods

$.ajax()	Performs an async AJAX request
$.ajaxPrefilter()	Handle custom Ajax options or modify existing options before each request is sent and before they are processed by $.ajax()
$.ajaxSetup()	Sets the default values for future AJAX requests
$.ajaxTransport()	Creates an object that handles the actual transmission of Ajax data
$.get()	Loads data from a server using an AJAX HTTP GET request
$.getJSON()	Loads JSON-encoded data from a server using a HTTP GET request
$.parseJSON()	Deprecated in version 3.0, use JSON.parse() instead. Takes a well-formed JSON string and returns the resulting JavaScript value
$.getScript()	Loads (and executes) a JavaScript from a server using an AJAX HTTP GET request
$.param()	Creates a serialized representation of an array or object (can be used as URL query string for AJAX requests)
$.post()	Loads data from a server using an AJAX HTTP POST request
ajaxComplete()	Specifies a function to run when the AJAX request completes
ajaxError()	Specifies a function to run when the AJAX request completes with an error
ajaxSend()	Specifies a function to run before the AJAX request is sent
ajaxStart()	Specifies a function to run when the first AJAX request begins
ajaxStop()	Specifies a function to run when all AJAX requests have completed
ajaxSuccess()	Specifies a function to run when an AJAX request completes successfully
load()	Loads data from a server and puts the returned data into the selected element
serialize()	Encodes a set of form elements as a string for submission
serializeArray()	Encodes a set of form elements as an array of names and values