Magical Scroll

Basic Usage

MagicalScroll.getInstance().addElement({
  target: "#scroll",
  animations: {
    opacity: {
      positions: [0, 100],
      values: [0, 1],
    },
  },
});

Magic Slugs

Slug	Description
#screenWidth	width of the screen
#screenHeight	height of the screen
#scrollWidth	width of the scroll container
#scrollHeight	height of the scroll container
#elementWidth	width of the element
#elementHeight	height of the element
#elementIn	when the element appear at the bottom of the container
#elementOut	when the element disappear at the top of the container
#elementCenter	when the element is placed center of the container
#parentElementWidth	width of the parent element (node)
#parentElementHeight	height of the parent element (node)
#parentElementIn	when the parent element (node) appear at the bottom of the container
#parentElementOut	when the parent element (node) disappear at the top of the container
#parentElementCenter	when the parent element (node) is placed center of the container
#ancestorElementWidth{1}	width of the ancestor element (node), where {1} means the generation(s)
#ancestorElementHeight{1}	height of the ancestor element (node), where {1} means the generation(s)
#ancestorElementIn{1}	when the ancestor element (node) appear at the bottom of the container, where {1} means the generation(s)
#ancestorElementOut{1}	when the ancestor element (node) disappear at the top of the container, where {1} means the generation(s)
#ancestorElementCenter{1}	when the ancestor element (node) is placed center of the container, where {1} means the generation(s)

Built-in Properties

Name	Description
opacity
scale
rotate
translateX
translateY
display	none or just nothing
visibility	visible or hidden
backgroundColor	calculating within values
color	calculating within values

Register/Replace your own property

Register/Replace the value populating callback

const magicalScroll = MagicalScroll.getInstance();
const animationName = "myScrollAnimation";
magicalScroll.registerPropertyPopulateCallback(
  animationName,
  (currentPosition, positions, values) => {
    const index = positions.findIndex((position) => position > currentPosition);
    return index > -1 ? values[index] : values[values.length - 1];
  },
);

Explanation

Name	Meaning
currentPosition	current scroll top of the container
positions	list of position which are already computed as a number
values	list of value

You can also register a new animation with existed built-in callback

const magicalScroll = MagicalScroll.getInstance();
const animationName = "opacity";
magicalScroll.registerPropertyPopulateCallback(
  animationName,
  MagicalScroll.populateNumberValueCallback,
);

Register/Replace the CSS generation callback

const magicalScroll = MagicalScroll.getInstance();
const animationName = "myScrollAnimation";
magicalScroll.registerPropertyPopulateCallback(
  animationName,
  (target, property, value) => {
    target.style.display = value ? null : "none";
  }
);

Explanation

Name	Meaning
target	element target
property	name of the property, animationName as the example above
value	computed value

What the next?

1. Provide other properties something like skew, brightness.
2. Interaction Observer API for better performance.
3. Support multiple instances.
4. Child slug.
5. Query for element.
6. Function of toggling class by position.
7. Inertia?
8. Animation function (ease-in-out, ... etc.) support.
9. Refactor it into better architecture.
10. Matrix calculation.