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https://github.com/shshaw/lengthy-svg
MicroLibrary for SVG Shape Length in a CSS Var
https://github.com/shshaw/lengthy-svg
Last synced: 17 days ago
JSON representation
MicroLibrary for SVG Shape Length in a CSS Var
- Host: GitHub
- URL: https://github.com/shshaw/lengthy-svg
- Owner: shshaw
- License: mit
- Created: 2018-01-30T13:31:48.000Z (almost 7 years ago)
- Default Branch: master
- Last Pushed: 2018-02-07T18:09:29.000Z (almost 7 years ago)
- Last Synced: 2024-04-27T21:34:07.491Z (7 months ago)
- Language: JavaScript
- Homepage:
- Size: 12.7 KB
- Stars: 67
- Watchers: 4
- Forks: 2
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# Lengthy
### _MicroLibrary for SVG Shape Length in a CSS Var_
Lengthy is a JavaScript microlibrary (1.2kb min, 0.7kb gzipped) to get the length of SVG shapes. The length will automatically be added to the element as a CSS Var to make it easy to do CSS animations of SVG `stroke-dashoffset` for the wonderful line drawing SVG technique and other interesting animations.
* [CSS Animation Demo](https://codepen.io/shshaw/pen/LeKKLd/)
* [JavaScript Animation Demo](https://codepen.io/shshaw/pen/JpowPb?editors=1010)
* [Shape Test](https://codepen.io/shshaw/pen/OQPEab)
---
## Installation
Add Lengthy to a projects with [npm](https://npmjs.org):
```
npm install -s lengthy-svg
```
For easy embedding on platforms like [Codepen](https://codepen.io), use [unpkg](https://unpkg.com)
```html
```
---
## Usage
Simply call `Lengthy` on a specific element, list of elements or a selector. The affected elements will receive a CSS var in their `style` and the `lengthy` class added.
_Input_
```html
```
_JavaScript_
```js
Lengthy("[data-lengthy]");
```
_Output_
```html
```
---
## CSS Animation
For a standard line-drawing animation, this is the CSS required.
It should be a relatively simple setup, but unfortunately, Chrome/Blink has a glitch with the CSS var animation keyframes. Chrome incorrectly treats a unitless `calc()`'d `var()` animation as a "discrete" animation, snapping to each value instead of transitioning between the values.
Firefox and Webkit/Blink all use unprefixed `animation-name`, so to target Webkit/Blink specifically, you'll use `-webkit-animation-name` for the override, then `-moz-animation-name` to override back for Firefox.
[CSS Animation Demo](https://codepen.io/shshaw/pen/LeKKLd/)
```css
.lengthy {
stroke-dasharray: var(--path-length) var(--path-length);
animation-duration: 3s;
animation-timing-function: cubic-bezier(0.5, 0, 0.5, 1);
animation-iteration-count: infinite;
animation-direction: alternate;
animation-name: stroke-move;
/* Override keyframes to fix a webkit glitch */
-webkit-animation-name: webkit-stroke-move;
/* Override yet again back to the original keyframes since Firefox obeys -webkit properties */
-moz-animation-name: stroke-move;
}
@keyframes stroke-move {
0%,
10% {
stroke-dashoffset: calc(1 * var(--path-length));
}
90%,
100% {
stroke-dashoffset: calc(-1 * var(--path-length));
}
}
/**
* Webkit does not support animating the stroke-dashoffset value _without_ a unit,
* so we have to deliver a separate keyframe list via -webkit-animation-name
*/
@keyframes webkit-stroke-move {
0%,
10% {
stroke-dashoffset: calc(1px * var(--path-length));
}
90%,
100% {
stroke-dashoffset: calc(-1px * var(--path-length));
}
}
```
---
## JavaScript Animation
Lengthy will return an array containing all the elements affected and their lengths if you want to use a JavaScript animation library like [TweenRex](https://github.com/tweenrex/tweenrex) or use the length data for other purposes.
[JavaScript Animation Demo](https://codepen.io/shshaw/pen/JpowPb?editors=1010)
```js
const targets = Lengthy(".stripe");
const tweens = targets.map(function(target) {
target.el.style.strokeDasharray = target.length;
return {
duration: 3000,
subscribe: tweenrex.interpolate({
targets: target.el,
strokeWidth: [2, 4, 2],
strokeDashoffset: [target.length, -target.length]
})
};
});
const t1 = TweenRex({
onFinish: function() {
t1.restart();
}
});
t1.add(tweens, { stagger: 500 });
t1.restart();
```