I want to send an email as soon as I click on html button. To do this task, I've written following code

HTML code:

<button onclick=sendEmail()>Send Email</button>

<p id=mailStatus></p>

Java Script Code:

function sendEmail()

{

     $.ajax({

           url: mail.php,

           type: POST,

           success: function(response) {

               if (!response) {

                    alert(Something went wrong. Please try again);

                    return;

               }



               var parsedJSON = eval('('+response+')');



               // If there's an error, display it.

               if(parsedJSON.Error) {

                  // Handle session timeout.

                  if (parsedJSON.Error == Timeout) {

                       alert(Session timed out. Please login again.);

                       window.location.reload();

                   }

                }

               document.getElementById('mailStatus').innerHTML = Email Sent successfully;  

            }

     });

}

The problem if when I click on Send Email button, I get an error message as

Uncaught ReferenceError: $ is not defined

Can someone please help??