Scroller

scroller.js

$.fn.scroller = function(offsetTop) {
    if (offsetTop == null) {
        offsetTop = 0;
    }

    this.each( function() {
        var id = this.id;

        $("a[href=#" + id + "]").on('click', function(event) {
            event.preventDefault();
            var distanceToTop = $(document.getElementById(id)).offset().top - offsetTop;
            if (distanceToTop != null) {
                $('html, body').stop().animate({ scrollTop: distanceToTop }, 1000);
            }
        });
    });
};

// USO: coloque o ID do alvo da âncora no href do link <a class="link-com-ancora" href="#id">ancora</a> e use o .scroller();

jQuery(document).ready(function($) {
    $('.link-com-ancora').scroller();
});