jQuery.ajax() method performs asynchronous http request and gets the data from the server. it allows you to send asynchronous http requests to submit or retrieve data from the server without reloading the whole page.
it can be used to send http GET, POST, PUT, DELETE etc. request. It can retrieve any type of response from the server.

Syntax: jQuery.ajax(url,[options])

Use option parameter to customize ajax request as per your need. All available options for configuring Ajax request can be listed below.

• accepts
• async
• beforeSend
• cache
• complete
• contentType
• crossDomain
• data
• dataType
• error
• global
• headers
• ifModified
• isLocal
• jsonp
• jsonpCallback
• mimeType
• password
• processData
• statusCode
• success
• timeout
• type
• url
• username
• xhr
• xhrFields

jQuery.ajax() is the all-encompassing Ajax request method provided by jQuery. It allows for the creation of highly-customized Ajax requests, with options for how long to wait for a response, how to handle a failure, whether the request is blocking (synchronous) or non-blocking (asynchronous), what format to request for the response, and many more options.

jQuery.get() is a shortcut method that uses jQuery.ajax() under the hood, to create an Ajax request that is typical for simple retrieval of information. Other pre-built Ajax requests are provided by jQuery, such as jQuery.post(), jQuery.getScript(), and jQuery.getJSON().

Efficiency of web page increases when minimized version of jQuery is used.min.js file will be more than 50% less than the normal js file. Reduction in the file size makes the web page faster.

The .detach() and .remove() methods are the same, except that .detach() retains all jQuery data associated with the removed elements and .remove() does not. .detach() is therefore useful when removed elements may need to be reinserted into the DOM at a later time.

The four parameters are

• URL – Need to specify the URL to send the request
• type – Specifies type of request(Get or Post)
• data – Specifies data to be sent to server
• Cache – Whether the browser should cache the requested page

The document.ready() event occurs when all HTML documents have been loaded, but window.onload() occurs when all content (including images) has been loaded. So generally the document.ready() event fires first.

Following are the basic selectors in jQuery:

• Element ID
• CSS Name
• Tag Name
• DOM hierarchy

If you want to display a welcome message or alert box then you have to add the following JavaScript in your file.

function setCookie(key, value) {
            var expires = new Date();
            expires.setTime(expires.getTime() + (1 * 24 * 60 * 60 * 1000));
            document.cookie = key + '=' + value + ';expires=' + expires.toUTCString();
        }

function getCookie(key) {
           var keyValue = document.cookie.match('(^|;) ?' + key + '=([^;]*)(;|$)');
           return keyValue ? keyValue[2] : null;
        }
if(getCookie('pop')==null)
{
	setCookie('pop',1);
	alert("WELCOME");
}

That’s it. In this code alert box shows only once per day.

Have any doubt, then comment here!