Smooth Scroll Plugin

Features

$.fn.smoothScroll

• Allows for easy implementation of smooth scrolling for same-page links.
• Works like this: $('a').smoothScroll();
• Specify a containing element if you want: $('#container a').smoothScroll();
• Exclude links if they are within a containing element: $('#container a').smoothScroll({excludeWithin: ['.container2']});
• Exclude links if they match certain conditions: $('a').smoothScroll({exclude: ['.rough','#chunky']});
• Adjust where the scrolling stops: $('.backtotop').smoothScroll({offset: -100});
• Add a callback function that is triggered before the scroll starts: `$('a').smoothScroll({beforeScroll: function() { alert('ready to go!'); }});
• Add a callback function that is triggered after the scroll is complete: $('a').smoothScroll({afterScroll: function() { alert('we made it!'); }});
• Add back button support by including a history management plugin such as Ben Alman's BBQ. See demo/bbq.html for an example of how to implement this.

Options

The following options, shown with their default values, are available for both $.fn.smoothScroll and $.smoothScroll:

{
  offset: 0,

  // one of 'top' or 'left'
  direction: 'top',

  // only use if you want to override default behavior
  scrollTarget: null,

  // fn(opts) function to be called before scrolling occurs.
  // `this` is the element(s) being scrolled
  beforeScroll: function() {},

  // fn(opts) function to be called after scrolling occurs.
  // `this` is the triggering element
  afterScroll: function() {},
  easing: 'swing',
  speed: 400,

  // coefficient for "auto" speed
  autoCoefficent: 2,

  // $.fn.smoothScroll only: whether to prevent the default click action
  preventDefault: true

}

The options object for $.fn.smoothScroll can take two additional properties: exclude and excludeWithin. The value for both of these is an array of selectors, DOM elements or jQuery objects. Default value for both is an empty array.

Setting options after initial call

If you need to change any of the options after you've already called .smoothScroll(), you can do so by passing the "options" string as the first argument and an options object as the second.

$.smoothScroll

• Utility method works without a selector: $.smoothScroll()

• Can be used to scroll any element (not just document.documentElement / document.body)

• Doesn't automatically fire, so you need to bind it to some other user interaction. For example:

    $('button.scrollsomething').on('click', function() {
      $.smoothScroll({
        scrollElement: $('div.scrollme'),
        scrollTarget: '#findme'
      });
      return false;
    });
  

• The $.smoothScroll method can take one or two arguments.

  • If the first argument is a number, the document is scrolled to that position. If it's an options object, those options determine how the document (or other element) will be scrolled.
  • If a number is provided as the second argument, it will override whatever may have been set for the scrollTarget option.

Additional Option

The following option, in addition to those listed for $.fn.smoothScroll above, is available for $.smoothScroll:

{
  // jQuery set of elements you wish to scroll.
  //  if null (default), $('html, body').firstScrollable() is used.
  scrollElement: null
}

$.fn.scrollable

• Selects the matched element(s) that are scrollable. Acts just like a DOM traversal method such as .find() or .next().
• The resulting jQuery set may consist of zero, one, or multiple elements.

$.fn.firstScrollable

• Selects the first matched element that is scrollable. Acts just like a DOM traversal method such as .find() or .next().
• The resulting jQuery set may consist of zero or one element.
• This method is used internally by the plugin to determine which element to use for "document" scrolling: $('html, body').firstScrollable().animate({scrollTop: someNumber}, someSpeed)

Notes

• To determine where to scroll the page, the $.fn.smoothScroll method looks for an element with an id attribute that matches the <a> element's hash. It does not look at the element's name attribute. If you want a clicked link to scroll to a "named anchor" (e.g. <a name="foo">), you'll need to use the $.smoothScroll method instead.
• The plugin's $.fn.smoothScroll and $.smoothScroll methods use the $.fn.firstScrollable DOM traversal method (also defined by this plugin) to determine which element is scrollable. If no elements are scrollable, these methods return a jQuery object containing an empty array, just like all of jQuery's other DOM traversal methods. Any further chained methods, therefore, will be called against no elements (which, in most cases, means that nothing will happen).