next-page-transitions

Simple and customizable page transitions for Next.js apps

Demo: https://next-page-transitions.now.sh/

What does this library do for me?

Simply put, it makes it easy to add page transitions to apps build with Next.js. It may work with other frameworks, but it was designed around the new App component and the way that Next.js handles pages. Specifically, it solves the problem of making sure only one page component is mounted at a time and that the next page isn't mounted until the previous one has completed its exit animation. It also has built-in support for showing a loading indicator if your page component has to load data before it can be shown.

Examples

If you prefer to learn by example, check out the examples directory for some Next.js apps that demonstrate how this library can be used.

Getting started

First, install the package:

npm install --save next-page-transitions

Next, ensure that your app has a custom App component; if not, follow the example on the Next.js readme to create one. Then, in your App's render method, wrap the page Component in a PageTransition component. You'll also have to define your own CSS classes that achieve the transition animations that you want. To keep this library simple and to account for the wide variety of ways that people produce and consume CSS, it doesn't offer any built-in styles and has no particular opinion about how the styles end up on your page. The example below has a simple transition that fades pages in and out.

import App, { Container } from 'next/app'
import React from 'react'
import { PageTransition } from 'next-page-transitions'

export default class MyApp extends App {
  static async getInitialProps({ Component, router, ctx }) {
    let pageProps = {}

    if (Component.getInitialProps) {
      pageProps = await Component.getInitialProps(ctx)
    }

    return { pageProps }
  }

  render() {
    const { Component, pageProps, router } = this.props
    return (
      <Container>
        <PageTransition timeout={300} classNames="page-transition">
          <Component {...pageProps} key={router.route} />
        </PageTransition>
        <style jsx global>{`
          .page-transition-enter {
            opacity: 0;
          }
          .page-transition-enter-active {
            opacity: 1;
            transition: opacity 300ms;
          }
          .page-transition-exit {
            opacity: 1;
          }
          .page-transition-exit-active {
            opacity: 0;
            transition: opacity 300ms;
          }
        `}</style>
      </Container>
    )
  }
}

When you move to a new page, the key prop will change, and the PageTransition component will detect that. Instead of immediately unmounting the page, it will apply the page-transition-exit class to a wrapper around the page to initialize the "exit" transition, and will then apply the page-transition-exit-active class as well to begin the transition. This is very similar to how the react-transition-group library does things. After the previous page has been animated out, the new page is mounted and a similar pair of .page-transition-enter and page-transition-enter-active classes will be applied. This process repeats every time a new page is navigated to.

Note: in previous versions of next-page-transitions, it wasn't necessary to specify the key prop on children of PageTransition. However, to make hot module reloading work correctly, it was necessary to make this prop required. Moving foward, children that don't specify a key prop will trigger a warning in the console. In the future, this may become a runtime error.

Support for delayed enters

Suppose you have a page that needs to make a network request before it can display its content. You could have the page itself render a loading spinner until it's ready to go, but then you lose the beautiful page transition animation you spent all that time perfecting. Luckily, this library makes it easy to handle that case.

If you add a static property pageTransitionDelayEnter = true to your page component, your page will be passed a special callback prop that you can use to indicate that everything has finished loading. In the meantime, your page will be mounted, but the enter transition won't be started yet, and a loading indicator of your choice will be shown in its place. When you call the callback prop, the loading spinner will be hidden, and your page will be animated into place! By default, the callback is passed via the pageTransitionReadyToEnter prop, but this can be specified by setting the loadingCallbackName prop on your PageTransition component.

Note: make sure that your component returns null from its render() function until it has finished loading its content and is ready to be animated in. Your page will still be in the React component tree while it's loading!

"But my network requests are usually fast!", you'll say. "They usually take only a few hundred milliseconds, and I don't want to flash a loading indicator on the screen for such a short period of time!" This library can handle that case as well. If you specify a loadingDelay prop, the loading indicator won't be shown until that much time has elapsed. If your component is ready to enter before then, the loading indicator will never be shown, keeping the UX clean and snappy. However, if your component is taking a long time, the loading indicator will be shown until your component is ready.

"That sounds kind of like the Placeholder concept from that React suspense talk. The one in this YouTube video." Yes, yes it does! That was the inspiration for this feature.

Here's an example component that simulates a network request with a timeout:

class About extends React.Component {
  static pageTransitionDelayEnter = true

  constructor(props) {
    super(props)
    this.state = { loaded: false }
  }

  componentDidMount() {
    this.timeoutId = setTimeout(() => {
      this.props.pageTransitionReadyToEnter()
      this.setState({ loaded: true })
    }, 2000)
  }

  componentWillUnmount() {
    if (this.timeoutId) clearTimeout(this.timeoutId)
  }

  render() {
    if (!this.state.loaded) return null
    return <div>Hello, world!</div>
  }
}

Assume for a moment that you have a Loader component that rendering a nice spinning loading indicator. You'll have to tell the PageTransition component that you want to use this component, and how long you want to wait until showing the network indicator:

<PageTransition
  timeout={300}
  classNames="page-transition"
  loadingComponent={<Loader />}
  loadingDelay={500}
  loadingTimeout={{
    enter: 400,
    exit: 0,
  }}
  loadingClassNames="loading-indicator"
>
  <Component {...pageProps} key={router.route} />
</PageTransition>

You'll also have to add styles if you want the loading indicator to be animated on/off the screen. If you want it to appear/disappear without any animation, you can add loadingTimeout={0} and omit the loadingClassNames property.

Check out the delayed-enter app under the examples directory for a complete example of what this looks like. The "About" page (pages/about.js) will wait 2 seconds before displaying its content, and in the meantime, the component at components/Loader.js will be displayed. Play around with the various delays to gain a deeper sense of how this component works.

`PageTransition` props

classNames: Specifies the class names that will be applied to the page wrapper to drive the page transition animations. Analogous to the classNames prop of react-transition-group's CSSTranstition component. However, note that only the string form of that prop is supported at present. Also, note that this library doesn't have a separate "appear" state; only "enter" and "exit" classes are needed.
tag: Specifies the tag or component that will be used to render the page wrapper. This element will receive the classNames prop. This is useful if you want to use semantic markup, e.g. if you want to render the page wrapper as main, or if you need to further customize the styling or behavior of the page wrapper.
timeout: Specifies timeouts for the page transition animations. Analogous to the timeout prop of react-transition-group's CSSTranstition component.
loadingComponent: A React element to be shown while
loadingDelay: The duration to wait before showing the loading indicator, in milliseconds. If a page finishes loading before this duration has elapsed, the loading component will never be shown. Defaults to 500ms.
loadingCallbackName: Specifies the name of the prop that your page will receive to call when it's done loading. Defaults to pageTransitionReadyToEnter
loadingTimeout: Analogous to the timeout prop of react-transition-group's CSSTranstition component. If this prop is set to 0, the loading indicator won't be animated on/off the screen.
loadingClassNames: Specifies the class names that will be applied to the loading component if one is specified. Analogous to the classNames prop of react-transition-group's CSSTranstition component.
monkeyPatchScrolling: By default, Next's Link component will scroll to the top of the page whenever it is clicked; this can have an undesirable jumpy effect when a page is transitioning out. If this prop is set to true when the component is mounted, then window.scrollTo will be monkey-patched so that programmatic scrolling can be disabled while a page is transitioning out. Defaults to false, since this potentially sketchy behavior should be opt-in.
skipInitialTransition: Specifies if page transition will be omitted on first mount. If you want to have transitions only between pages, not on first page load, set skipInitialTransition to true. By default, skipInitialTransition is set to false.

Contributing

PRs are welcome! Before working on and submitting a PR, please make an issue describing the feature you want to build. It may be outside the scope of this project, or a maintainer might already be working on it.

illinois/next-page-transitions