Uncaught ReferenceError: $ is not defined Page.aspx

I want to READ list data from with the help of RESTAPI in SharePoint. I use below code to do the operation.

<script src="http://ift.tt/1dW8QIk"></script>
<script type="text/javascript">

function getListItemById(webUrl,listName, itemId, success, failure) {
    var url = webUrl + "/_vti_bin/listdata.svc/" + listName + "(" + itemId + ")";
    $.ajax({
        url: url,
        method: "GET",
        headers: { "Accept": "application/json; odata=verbose" },
        success: function (data) {
            success(data.d);
            alert('Success');
        },
        error: function (data) {
            failure(data.responseJSON.error);
        }
    });
}


//Usage
getListItemById('http://ctv-test', 'RESTList', 2, function (taskItem) {
    console.log(taskItem.TaskName); 
  },
  function(error){
    console.log(JSON.stringify(error));
  }
);
</script>

When I execute my code I get below 2 errors in browser console.

Uncaught ReferenceError: $ is not defined Page.aspx

Uncaught TypeError: Cannot read property 'parentElement' of null