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scrollit

September 6, 2015

Scrollit | jQuery plugin for Parallax, Tweening and Waypoints.

ScrollIt is a simple scroll animations jQuery plugin to create Parallax, Tweening and Waypoints

Created by rorymurphy

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Scrollit jQuery plugin

parallax

ScrollIt

Simple scroll animations including Parallax, Tweening and Waypoints

Demo page: http://rorymurphy.github.io/scrollit/

ScrollIt is a client-side JavaScript library that provides easy to use jQuery extensions for implementing common scroll based animations, as well as declarative data attributes where possible. The only dependency is jQuery, and the animations work across desktop and mobile.

Parallax

Parallax allows the appearance of depth to be created in a website by moving objects at different speeds relative to each other. Parallax is most often done using the background image but can also be done using any DOM object. However, parallaxing DOM objects can cause redraw events which, depending on the browser, may make the experience sub-optimal. There are two ways to invoke parallax using ScrollIt. The first uses a declarative HTML data attribute.

  <div style="position: relative;" data-parallax="0.5">Some content...</div>

In this example, the element will move at 1/2 the scroll speed it normally would. It is important to note that, in order for parallaxing to work correctly, the element must be a positioned element (preferably position: relative); This method parallaxes by moving the element itself, as opposed to the background image, which is also commonly the target of parallax. To use more advanced options of this sort, we can call the parallax jQuery extension directly. This same call can be written as below:

  <div class="parallax-me" style="position: relative;">Some content...</div>
  <script type="text/javascript">
    $('.parallax-me').parallax({
      axis: 'y',
      attr: 'top',
      speed: 0.5
    });
  </script>

The attributes available are

Attribute Possible Values Description
axis 'y' or 'x' Parallaxing can be done in either the vertical or horizontal scroll directions
attr usually 'top' or 'background-position-y' but could be any CSS attribute accepting pixel values The parallax engine will calculate an offset to be applied to the element, based on its position. The attribute instructs the parallax engine what as to what CSS attribute this offset should be applied.
speed -infinity < speed < infinity How much slower than normal scroll the object should move, 0 = normal scroll, 0 < speed < 1 = normal parallax , 1 = fixed position, > 1 backwards scroll

Tweening

Tweening is a technique that allows elements to be animated by specifying a start value, and end value and an easing function. The tweening engine can then animate the transition from one to the other. ScrollIt supports tweening on any color CSS attribute color (rgb, rgba, hsl or hsla) or any attribute that contains or a number, and not just strictly numeric values (more on that in a minute). A tweening call looks like:

  <div id="color-me"></div>
  <div id="next-div"></div>
  <script type="text/javascript">
      $('#color-me').tween({
         start: 0,
         end: $('#next-div'),
         easing: 'easeInCubic',
         styles: {
             'background-color': '#ff0000'
         }
      });
  </script>

So what is this tween doing? This particular tween is changing the background-color of the "color-me" div from it's start color (whatever that is based on the CSS, since no start value was specified) to #ff0000. It will do this from scroll position 0 (of the scrollParent element) until the top of the "#next-div" element reaches the top of the screen.

Many of the options for a tween allow for a selection of datatypes to be passed in

Option Datatype Common Values Description
axis string 'y' or 'x' Tweening can be done in either the vertical or horizontal scroll directions
start number When a number is specified, it refers to the absolute scroll position relative to the scrollParent.
string 'top', 'bottom', 'left' or 'right' The start value will be set to the appropriate edge of the scrollParent
jQuery object The start value will be set to the Top (y-axis) or Left (x-axis) of the first element in the jQuery set
function An arbitrary function can be provided that will return the numeric value for the start. This function is reevaluated on each scroll event, so the start value can be dynamic when a function is provided
end number same as start, but the position at which the tweening ends
string 'top', 'bottom', 'left' or 'right' The start value will be set to the appropriate edge of the scrollParent
jQuery object same as start, but the position at which the tweening ends
function same as start, but the position at which the tweening ends
easing string The name of the easing function to use. ScrollIt provides the same easing functions as jQuery UI. See https://jqueryui.com/easing/ for more details.
function Specifies a custom easing function to use. The function must accept a single argument with a range from 0 (beginning) to 1 (end). Additionally, the functions return value should be 0 at point 0 and 1 at point 1, although it may go below 0 or above 1 in-between (see easeOutElastic as an example).
styles object The styles option accepts an object where the keys are the CSS attributes to tween and the values are either a) just the end value of the tween or b) a JavaScript object that contains start value and end value in the form {'background-color' : {startValue: '#000000', endValue: '#ffffff'} }

Many more advanced options are available. For example:

  <div id="color-me"></div>
  <div id="next-div"></div>
  <script type="text/javascript">
      $('#color-me').tween({
         start: function(){
           return $('#color-me').offset().top - $(window).height() / 2;
         },
         end: $('#next-div'),
         easing: 'easeInCubic',
         styles: {
             'transform': {startValue: 'rotate(0deg)', endValue: 'rotate(720deg)'}
         }
      });
  </script>

This variation specifies the start using a function that returns a position at which the tween should begin. This is a very powerful way to control the space in which tweening should occur, and often desireable for responsive designs, where the pixel heights of elements change based on screen size. Also, in this example, both a start value and an end value are specified, and the values are not strictly numeric. In this circumstance, ScrollIt tries to find the number within the two values and then tweens it, generating a string for 'rotate(10deg)', 'rotate(90deg)', etc. for each point along the way.

Waypoints

Waypoints are an easy way to specify that some action be taken when the scroll position reaches a certain point. The waypoint can be specified relative to any element, such as 100px above a particular element (even if that element is itself moving or changing size). At the same time, specifying the waypoint relative to the document element will yield a fixed position waypoint. The basic syntax to invoke a waypoint is

  <img id="someimage" src="..." />
  <script type="text/javascript">
    $(document).waypoint({
       position: 500,
       down: function(){
           var img = $('#someimage');
           img.slideDown();
       },
       up: function(){
           var img = $('#someimage');
           img.slideUp();
       }

    });
  </script>

From this example, we can see that the primary options to provide are a position, and a down method and/or an up method. Like most options in ScrollIt, the position option can be either a value or a function that returns a position value.

Option Datatype Common Values Description
axis string 'y' or 'x' Waypoints can be set on either the vertical or horizontal scroll directions
position number The scroll position at which to trigger the waypoint
string 'top', 'bottom', 'left' or 'right' The start value will be set to the appropriate edge of the scrollParent
function A function that returns a position at which to trigger the waypoint. This is particularly powerful when you want to set a waypoint relative to a (potentially dynamic) element.
down function A function to trigger when the waypoint is passed moving downward
up function A function to trigger when the waypoint is passed moving upward
right function A function to trigger when the waypoint is passed moving to the right
left function A function to trigger when the waypoint is passed moving to the left

Sample

The ScrollIt repo includes a test directory that contains a very simple (and ugly) demonstration of many of the core features.

License

The MIT License (MIT)

Copyright (c) 2015 Rory Murphy

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

scrollit

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