how to scroll in pixels code example

Example 1: jquery on scroll x pixels

$(document).scroll(function() {

        if ( $(document).scrollTop() >= 1000 ) {
        } else if ( $(document).scrollTop() >= 500 ) {
        } else {
        }
    });

Example 2: jquery on scroll x pixels

$(document).scroll(function() {
               var value=$(document).scrollTop();

                if ( value >= 1000 ) { /*do this*/; return;}
                if ( value >= 500 ) { /*do this*/; return;}
                if ( value >= 150 ) { /*do this*/; return;}
                if ( value >= 30 ) { /*do this*/; return;}
                /* else */
                /*do this*/
            });