@castlenine/svelte-aoe

@castlenine/svelte-aoe uses the Intersection Observer API to detect when an element enters the viewport.

When the element enters the viewport, @castlenine/svelte-aoe applies a class that triggers a CSS animation.

Demo

Installation

Use your package manager to install:

npm i @castlenine/svelte-aoe

Setup

1. Import and add the component once in your root layout:

File: src/routes/+layout.svelte

<script>
  import AnimateOnEnter from '@castlenine/svelte-aoe';
</script>

<AnimateOnEnter />

<slot />

1. Add a data-aoe attribute to any element you want to animate:

<img data-aoe="fade-up" src="https://dummyimage.com/500x300"/>

Elements are automatically detected, including those added dynamically by page navigation.

Animations

Normal speed

• up
• right
• left
• down
• fade
• fade-up
• fade-right
• fade-left
• fade-down

Fast speed

• up-fast
• right-fast
• left-fast
• down-fast
• fade-fast
• fade-up-fast
• fade-right-fast
• fade-left-fast
• fade-down-fast

Slow speed

• up-slow
• right-slow
• left-slow
• down-slow
• fade-slow
• fade-up-slow
• fade-right-slow
• fade-left-slow
• fade-down-slow

Normal speed partial fade

Starts with 0.25 opacity

• partial-fade
• partial-fade-up
• partial-fade-right
• partial-fade-left
• partial-fade-down

Fast speed partial fade

Starts with 0.25 opacity

• partial-fade-fast
• partial-fade-up-fast
• partial-fade-right-fast
• partial-fade-left-fast
• partial-fade-down-fast

Slow speed partial fade

Starts with 0.25 opacity

• partial-fade-slow
• partial-fade-up-slow
• partial-fade-right-slow
• partial-fade-left-slow
• partial-fade-down-slow

You can add your own animations by following the same pattern in your CSS.

[data-aoe='your-animation'] {
  transform: translateX(-45px);
  transition:
    transform 600ms,
    opacity 900ms;

  &.aoe {
    transform: translateX(0);
    transition-delay: 0s;
  }
}

Properties

Property name	Type	Default value
root	Document, Element, null, undefined	null
rootMargin	string in pixels (px) or percentage (%)	0px
threshold	number, number[] between 0 and 1.0	0.3

root is the element used as the viewport for checking the visibility of the target. It must be an ancestor of the target. If not specified or if set to null, it defaults to the browser viewport.

rootMargin is the margin around the root. It can have values similar to the CSS margin property, e.g., "10px 20px 30px 40px" (top, right, bottom, left). The values can be percentages. The default is '0px' (no margin).

threshold is either a single number or an array of numbers, indicating at what percentage of the target's visibility the observer's callback should be executed. A value of 0.0 or 0 indicates that even a single pixel of the target is visible. A value of 1.0 or 1 requires the target to be completely visible. The default is 0.3 (30%).

Scoped Overrides

Set defaults for all data-aoe elements within a page or section using data-aoe-scope on a container element, or the <AnimateOnEnterScope> convenience component. Elements inside a scope inherit its values unless they have their own per-element data-aoe-* overrides.

Using the data-aoe-scope attribute

<div data-aoe-scope data-aoe-threshold="0.5" data-aoe-root-margin="20px">
  <!-- All elements inside use threshold=0.5 and rootMargin=20px -->
  <img data-aoe="fade-up" src="..." />

  <!-- Per-element overrides still take priority -->
  <img data-aoe="fade-up" data-aoe-threshold="0.8" src="..." />
</div>

Using the <AnimateOnEnterScope> component

<script>
  import { AnimateOnEnterScope } from '@castlenine/svelte-aoe';
</script>

<AnimateOnEnterScope threshold={0.5} rootMargin="20px">
  <img data-aoe="fade-up" src="..." />
</AnimateOnEnterScope>

Property name	Type	Default value
root	CSS selector string	undefined
rootMargin	string in pixels (px) or percentage (%)	undefined
threshold	number between 0 and 1.0	undefined

Scopes can be nested. The innermost scope takes precedence.

Per-Element Overrides

Individual elements can override scope or global properties using data-aoe-* attributes. If an attribute is not set, the value from the nearest data-aoe-scope ancestor is used, then <AnimateOnEnter />, and then the package default.

Attribute	Type	Overrides
data-aoe-threshold	number between 0 and 1.0	threshold
data-aoe-root	CSS selector string	root
data-aoe-root-margin	string in pixels (px) or percentage (%)	rootMargin

Examples

<!-- Uses global defaults -->
<img data-aoe="fade-up" src="..." />

<!-- Overrides threshold only (animates as soon as 1px is visible) -->
<img data-aoe="fade-up" data-aoe-threshold="0" src="..." />

<!-- Overrides rootMargin only (triggers 200px before entering the viewport) -->
<img data-aoe="fade-up" data-aoe-root-margin="200px" src="..." />

<!-- Overrides root to a specific scroll container -->
<img data-aoe="fade-up" data-aoe-root="#scroll-container" src="..." />

<!-- Multiple overrides -->
<img data-aoe="fade-up" data-aoe-threshold="0.8" data-aoe-root-margin="50px" src="..." />

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Inspired by Animate on Scroll and forked from lliamscholtz/svelte-aoe