Using jQuery to see if a div has a child with a certain class

There is a hasClass function

if($('#popup p').hasClass('filled-text'))

You can use the find function:

if($('#popup').find('p.filled-text').length !== 0)
   // Do Stuff

Simple Way

if ($('#text-field > p.filled-text').length != 0)

Use the children funcion of jQuery.

$("#text-field").keydown(function(event) {
    if($('#popup').children('p.filled-text').length > 0) {
        console.log("Found");
     }
});

$.children('').length will return the count of child elements which match the selector.