Smooth scrolling in jquery on all anchors

$(function() {
  $(document).on('click', 'a[href^="#"]', function(e) {
    // target element id
    var id = $(this).attr('href');

    // target element
    var $id = $(id);
    if ($id.length === 0) {
      return;
    }

    // prevent standard hash navigation (avoid blinking in IE)
    e.preventDefault();

    // top position relative to the document
    var pos = $id.offset().top;

    // animated top scrolling
    $('body, html').animate({scrollTop: pos});
  });
});

//for drupal:

Drupal.behaviors.smoothHrefScroll = {
    attach: function (context) {
      // handle links with @href started with '#' only
      $(document).on('click', 'a[href^="#"]', function(e) {
        // target element id
        var id = $(this).attr('href');

        // target element
        var $id = $(id);
        if ($id.length === 0) {
          return;
        }

        // prevent standard hash navigation (avoid blinking in IE)
        e.preventDefault();

        // top position relative to the document
        var pos = $id.offset().top;

        // animated top scrolling
        $('body, html').animate({scrollTop: pos});
      });
    }
  };