Question

how can I add a class when mouse is over an element?

var row = $('<tr></tr>')
    .append('<td class="list_row">'+js2txt(string)+'</td>')
    .mouseover(function(){
        this.addClass('list_row_mover');
    });

js error:

this.addClass is not a function

Answer 1

In your function the scope (this) is the HTML element, not the jQuery object.

Here is a possible fix:

var row = $('<tr></tr>')
  .append('<td class="list_row">'+js2txt(string)+'</td>')
  .mouseover(function(){
    $(this).addClass('list_row_mover');
  });