how to make an ajax call in javascript code example

Example 1: ajax exmaple\

$.ajax({
    url:'your url',
    type: 'POST',  // http method
    data: { myData: 'This is my data.' },  // data to submit
    success: function (data, status, xhr) { // after success your get data
        $('p').append('status: ' + status + ', data: ' + data);
    },
    error: function (jqXhr, textStatus, errorMessage) { // if any error come then 
            $('p').append('Error' + errorMessage);
    }
});

Example 2: ajax syntax in javascript

var id = empid;

$.ajax({
    type: "POST",
    url: "../Webservices/EmployeeService.asmx/GetEmployeeOrders",
    data: "{empid: " + empid + "}",
    contentType: "application/json; charset=utf-8",
    dataType: "json",
    success: function(result){
        alert(result.d);
        console.log(result);
    }
});

Example 3: js functional ajax requests

function checkUserIdExists(userid, callback) {
        return $.ajax({
        url: 'theurl',
        type: 'GET',
        cache: false,
        data: {
           userid: userid
        }
    })
    .done(callback)
    .fail(function(jqXHR, textStatus, errorThrown) {
        // Handle error
    });
}

checkUserIdExists(2, function(data) {
    console.log(data); // Do what you want with the data returned
});