react-plx

React component, for creating on scroll effects aka. parallax. Lightweight, yet powerful.
Version 2 brings even more performance improvements and TypeScript support.

• v2.0.0 breaking changes

- px units are not assumed and need to be provided manually - ~tagName prop was removed~ it was returned in v2.1.0
Changelog

Demo

Check the live demo. You can find source for the demo here.

I would really like to see what you people have built using Plx and create a showcase section. So please open an issue titled Showcase: <your awesome stuff> so it can be featured. Cheers!

Quick start

Get it from npm

$ npm install --save react-plx

Import and use it in your React app.

import React, { Component } from "react";
import Plx from "react-plx";

// An array of parallax effects to be applied - see below for detail
const parallaxData = [
  {
    start: 0,
    end: 500,
    properties: [
      {
        startValue: 1,
        endValue: 2,
        property: "scale",
      },
    ],
  },
];

class Example extends Component {
  render() {
    return (
      <Plx className="MyAwesomeParallax" parallaxData={parallaxData}>
        /* Your content */
      </Plx>
    );
  }
}

Table of contents

• Plx - React Parallax component

- Demo - Quick start - Table of contents - What is this? - Props

- [parallaxData](#parallaxdata)
- [properties](#properties)

- Example of props - Animation state CSS classes - Browser support - License

What is this?

This is React component which makes creating on scroll effects (aka parallax) easy. If you are not sure what it does, demo should help.
It is lightweight, and beside react, react-dom and prop-types has no dependencies, now it has small bezier-easing package. As listening to scroll event is not performant, this component uses different approach. Interval is set (every 16ms to get 60fps) to check if scroll position is changed, and if it is, it broadcasts custom event. All of the Plx components are sharing the scroll manager singleton. Interval is set when the first component is created, and cleared when last one is unmounted. Interval time can be changed through the props, but it is shared across the components.
Elements outside of viewport are not animated. This is done by using getBoundingClientRect, but there is a known bug in iOS with getBoundingClientRect and position fixed. If you get into the same problems, you can force rendering by passing animateWhenNotInViewport={ true }.
Still you need to avoid common "don't dos" when making a parallax page:

• Avoid background-size: cover
• Don’t animate massive images or dramatically resize them
• Avoid animating 100 things at once
• Only use properties that are cheap for browsers to animate - opacity and transform (translate, rotate, skew, scale)

Read this great article to find out more (that is where I got my initial inspiration).
Of course, you can break any of these rules, but test for performance to see if it works for you.
Component is written as ES module, so it will work with webpack and other module bundlers (which is standard for React apps anyway). Tested with react-create-app and my boilerplate, Marvin.
Read more about how it works in this blog post.

Props

• className string

CSS class name (it will be applied along with Plx class name).

• style object

CSS style object, please note that properties used in parallax will be overridden by component.

• animateWhenNotInViewport bool, default false

If set to true element will be animated even when it is not in the viewport. This is helpful with fixed elements in iOS due to know bug with getBoundingClientRect in iOS.

• disabled boolean

When true disabled animation completely.

• freeze bool, default false

When true animation will be stopped at current state when condition is met.

• parallaxData array of items (item structure described beneath), required

Main data, describes parallax segments.

• onPlxStart function

If set, the Plx component will call this function each time the animation state changes to active. (refer to animation state CSS classes)

• onPlxEnd function

If set, the Plx component will call this function each time the animation state changes from active to another state. (refer to animation state CSS classes)

• tagName string, default "div"

HTML or SVG element tag name to be used.
Any other props will be passed to the component (for example this is useful for aria-* props).

parallaxData

• start number, string, HTMLElement, required

Scroll position where parallax effect should start. Can one of the following:
- Number - value in pixels - String

- Value in px, vh or % (`50px`, `50%`, `25vh`). Percentage is calculated out of max page scroll.
- CSS Selector (`.my-element`, `#some-id`) to be used with `document.querySelector`.
- `"self"` component's element will be used

- HTMLElement, given element will be used.
For element, selector and "self" animation will start when that element enters the viewport. You can use startOffset prop to offset start position.
Example:
```js start: 100; // starts when scroll hits 100px start: "self"; // starts when plx's element enters the viewport start: ".start-element"; // starts when .start-element enters the viewport ```
PLEASE NOTE that parallaxData should be sorted by start value!

• end number, string, HTMLElement

Scroll position where parallax effect should end. It has higher priority than duration. Can one of the following:
- Number - value in pixels - String

- Value in px, vh or % (`50px`, `50%`, `25vh`). Percentage is calculated out of max page scroll.
- CSS Selector (`.my-element`, `#some-id`) to be used with `document.querySelector`.
- `"self"` component's element will be used

- HTMLElement, given element will be used.
For element, selector and "self" animation will end when that element enters the viewport. You can use endOffset prop to offset end position.
Example:
```js end: 300; // ends when scroll hits 300px end: "self"; // ends when plx's element enters the viewport end: ".end-element"; // ends when .end-element enters the viewport ```

• duration number, string, HTMLElement

How long should effect last (it will finish when scroll position equals start + duration). It will be used if end is not defined. Can one of the following:
- Number - value in pixels - String

- Value in px, vh or % (`50px`, `50%`, `25vh`). Percentage is calculated out of max page scroll.
- CSS Selector (`.my-element`, `#some-id`) to be used with `document.querySelector`.

- HTMLElement, given element will be used.
For element and selector, element's height will be used as duration. Any other string will be considered CSS selector and it will be used with document.querySelector.
Example:
```js duration: 300; // animation will last for 300px duration: ".duration-element"; // animation will last for .duration-element's height ```

• startOffset number, string

Start offset, can be a number or string value in px, vh or % (50px, 50%, 25vh).

• endOffset number, string

End offset, can be a number or string value in px, vh or % (50px, 50%, 25vh).

• easing string, function or array, default: 'linear'

Easing function, you can pass the name (string) to choose one of the built-in functions. Built-in easing functions are:
- ease - easeIn - easeOut - easeInOut - easeInSine - easeOutSine - easeInOutSine - easeInQuad - easeOutQuad - easeInOutQuad - easeInCubic - easeOutCubic - easeInOutCubic - easeInQuart - easeOutQuart - easeInOutQuart - easeInQuint - easeOutQuint - easeInOutQuint - easeInExpo - easeOutExpo - easeInOutExpo - easeInCirc - easeOutCirc - easeInOutCirc
Cubic beziers are supported, pass an array to it with four points of your custom bezier (you can copy CSS beziers).
```js easing: 0.25, 0.1, 0.53, 3; ```
You can even pass custom function which accepts one argument, which will be number from 0 to 1.
```js // Define your custom easing const myCustomEasing = (x) => {

return x * x;

};
...
// and then pass it to Plx easing: myCustomEasing ```

• name string (without spaces)

Name used in animation state CSS classes

• properties array of items (item structure described beneath), required

List of properties to be animated

properties

• property string, required

CSS property to be animated, works only on properties which accept numerical values (e.g. opacity, height...). For transform use function names instead (e.g. translateX, scale, rotate...). Same goes for filters.
For properties that use pixels (height, width, margin...), please be sure to provide unit: "px" prop.
Supported transform functions are:
- translateX - translateY - translateZ - skew - skewX - skewY - skewZ - rotate - rotateX - rotateY - rotateZ - scale - scaleX - scaleY - scaleZ
Supported colors are:
- backgroundColor - borderBottomColor - borderColor - borderLeftColor - borderRightColor - borderTopColor - color - fill - stroke
Supported CSS filters are:
- blur - brightness - contrast - grayscale - hueRotate - invert - opacityFilter (as it shares the same name as CSS opacity) - saturate - sepia
To keep you parallax effects performant, I strongly advice not to use anything but opacity and transforms. Some filters should be cheap as well, with blur being the most expensive out of supported filters.

• startValue number (or string for color), required

Start value for the effect. Property will have this value when scroll position equals parallaxData.start. For colors supported formats are: #123, #001122, rgb(0,0,255) and rgba(0,0,255,0.5).

• endValue number (or string for color), required

End value for the effect. Property will have this value when scroll position equals parallaxData.end. For colors supported formats are: #123, #001122, rgb(0,0,255) and rgba(0,0,255,0.5).
Between parallaxData.start and parallaxData.end value will transition relative to scroll position.

• unit string

CSS unit (e.g. %, rem, em...) to be applied to property value. For transforms and filters library is using pixels and degrees by default. For everything else please provide appropriate units (i.e. "px" for "height").

Example of props

These are the exact props used in this example.

const exampleParallaxData = [
  {
    start: 0,
    end: 300,
    properties: [
      {
        startValue: 0,
        endValue: 90,
        property: "rotate",
      },
      {
        startValue: 1,
        endValue: 1.5,
        property: "scale",
      },
      {
        startValue: 1,
        endValue: 0.75,
        property: "opacity",
      },
    ],
  },
  {
    start: 350,
    duration: 300,
    properties: [
      {
        startValue: "#3cb99c",
        endValue: "rgba(50,50,200,0.8)",
        property: "backgroundColor",
      },
      {
        startValue: 0,
        endValue: 100,
        property: "translateY",
      },
      {
        startValue: 0.75,
        endValue: 1,
        property: "opacity",
      },
    ],
  },
  {
    start: 700,
    duration: 1000,
    properties: [
      {
        startValue: 100,
        endValue: 0,
        property: "translateY",
      },
      {
        startValue: 1.5,
        endValue: 2,
        property: "scale",
      },
      {
        startValue: 90,
        endValue: 0,
        property: "rotate",
      },
      // Blur is not performant
      // Used just as an example for CSS filters
      {
        startValue: 0,
        endValue: 20,
        property: "blur",
      },
    ],
  },
];

Animation state CSS classes

Component will also apply CSS classes that match current animation state. Classes are:

• Plx--above

scroll position is above first start position (animation isn't started yet)

• Plx--below

scroll position is below last end position (animation is finished)

• Plx--active

scroll position is below first start and last end position (animation is in progress, including between states)

• Plx--in Plx--in-{n}

scroll position is in n-th segment (Plx--in-0, Plx--in-1...). If name prop is passed (see above) it will be used instead of index (Plx--in-superDuperName).

• Plx--between Plx--between-{a}-and-{b}

scroll position is between segments a and b (Plx--between-0-and-1, Plx--between-1-and-2...) If name prop is passed (see above) it will be used instead of index (Plx--between-superDuperName-and-anotherName).
active class is applied along with both in and between classes.

Browser support

All modern browsers.
Since version 2, I'm not supporting nor testing it in Internet Explorer. Library will probably work in IE10+ and even IE9 should work if you provide a polyfill for requestAnimationFrame.

License

Released under MIT License.