How to addclass with timeout

Question

Don't know why it's not working, i think the code is fine - could you tell me what is wrong? I need to add some class after some time interval...

$('.main_menu ul li').mouseenter(function(){
    setTimeout(function(){
        $(this).children('.sub_menu_main').addClass('opened')
    },200);
});
$('.main_menu ul li').mouseleave(function(){
    $(this).children('.sub_menu_main').removeClass('opened')
});

Answer 1

$('.main_menu ul li').on({
    mouseenter: function(){
        var self = this; //in scope
        $(self).data('timer', setTimeout(function(){ //new scope
            $(self).children('.sub_menu_main').addClass('opened'); //out of scope
        },200);
    },
    mouseleave: function(){
        clearTimeout($(this).data('timer'));
        $(this).children('.sub_menu_main').removeClass('opened');
    }
});