how to add to the value of a input via jquery code example

Example 1: how to get a value using jquery

//for imput field given in HTML

<input type="text" id="myid" class="myclass" >
  
// Using ID to find value
  
$("#myid").val();

// Using Class to find value

$(".myclass").val();

Example 2: jquery set textbox value

$.get('compz.php?prodid=' + x + '&qbuys=' + y, function(data) {
    $('#subtotal').val(data);
});