Question

I have the following script which works as long as it is returned data:

$(document).ready(function() {
    $.ajax({
        type: 'POST',
        url: 'notifications.asmx/GetNotifications',
        data: '{strUser: "pqr"}',
        contentType: 'application/json; charset=utf-8',
        dataType: 'json',
        success: function( notifications ) {
            if( notifications !== null ) { //<-- this makes no difference
                 alert( notifications.d[0].text ) ;
            } else {
                alert ( "null" );
            }
        },
        error: function(xhr, status, error) {
                 var err = eval("(" + xhr.responseText + ")");
                 alert(err.Message) ;
        }
    });
});

If data is not returned, I get the error:

Uncaught TypeError: Cannot read property 'text' of undefined

I have tried wrapping it in various if statements checking for null values, but that does not make any difference.

Answer 1

It sounds like it’s notifications.d[0] that is undefined so you should be checking that in your if statement rather than notifications.

if( notifications.d[0] ) { //<-- this should now work
    alert( notifications.d[0].text ) ;
} else {
    alert ( "null" );
}