multiple javascript code in one file

How do I set up a Javascript file with multiple bits of code? When ever I add existing code to my file it cancels out the first bit.

I know it's probably something really simple.

var main = function() {

/* Push the body and the nav down by 130px */ $('.menu-icon').click(function() { $('.nav_links').animate({ top: "0px" }

, 400);

$('body').animate({
  top: "700px"
}, 400);

});

/* Then push them back */ $(a).click(function() { $('.menu').animate({ top: "-700px" }, 400);

$('body').animate({
  top: "0px"
}, 400);

});

};

$(document).ready(main);

$(document).ready(function() { // Scroll the whole document $('body').localScroll({ target:'body' });

        }); 

        $(document).ready(function() {

            $('.nav_links li a').click(function(e) {

                $('.nav_links li a').removeClass('active');

                var $parent = $(this);

                if (!$parent.hasClass('active')) {

                    $parent.addClass('active');

                }

                e.preventDefault();
            });

        });

        $(document).ready(main);