README.md

rrr-lazy

Lazy load component with react && react-router.

Installationg

rrr-lazy requires React 16.2.0 or later.

For npm:

npm install rrr-lazy

For yarn:

yarn add rrr-lazy

IntersectionObserver is required by this library. You can use this polyfill for old browsers https://github.com/w3c/IntersectionObserver/tree/master/polyfill

Usage

Use as a common lazy component

import React from 'react';
import { Lazy } from 'rrr-lazy';

const MyComponent = () => (
  <div>
    <Lazy
      rootMargin="300px 0 300px 0"
      render={(status) => (
        if (status === 'unload') {
          return <div>Unload</div>
        }
        if (status === 'loading') {
          return <div>Loading</div>
        }
        if (status === 'loaded') {
          return (
            <img
              style={{ height: 762, width: 1024 }}
              src={ status === 'loaded' ? 'http://apod.nasa.gov/apod/image/1502/HDR_MVMQ20Feb2015ouellet1024.jpg' : `data:image/svg+xml,${encodeURIComponent('<svg xmlns="http://www.w3.org/2000/svg"/>')}`}
            />
          );
        }
        throw new Error('Unknown status');
      )}
    />
  </div>
);

Loading data or do something else with lifecycle hooks

import { lazy } from 'rrr-lazy';

async function onLoading() {
  // Loading data;
  // ...
  return data;
}
async function onLoaded() {
  // Do something on loaded
  // ...
  return result;
}

async function onUnload() {
  // Do something on unload
  // ...
  return result;
}

async function onError(error) {
  // Do something on error
  console.error(error);
  // ...
  return result;
}

class App extends React.Component {
  render() {
    // the matched child route components become props in the parent
    return (
      <Lazy
        rootMargin="300px 0 300px 0"
        render={(status) => (
          if (status === 'unload') {
            return <div>Unload</div>
          }
          if (status === 'loading') {
            return <div>Loading</div>
          }
          if (status === 'loaded') {
            return (
              <img
                style={{ height: 762, width: 1024 }}
                src={ status === 'loaded' ? 'http://apod.nasa.gov/apod/image/1502/HDR_MVMQ20Feb2015ouellet1024.jpg' : `data:image/svg+xml,${encodeURIComponent('<svg xmlns="http://www.w3.org/2000/svg"/>')}`}
              />
            );
          }
          throw new Error('Unknown status');
        )}
        onLoading={onLoading}
        onLoaded={onLoaded}
        onUnload={onUnload}
        onError={onError}
    />
    )
  }
}

API: <Lazy root rootMargin render loaderComponent loaderProps onError onLoaded onUnload onUnloaded />

Props

root

Type: String|HTMLElement Default: null

This value will be used as root for IntersectionObserver (See root.

rootMargin

Type: String Default: null

This value will be used as rootMargin for IntersectionObserver (See rootMargin.

render(status, props)

Type: Function Required

status can be unload, loading, loaded.

props are props that passed from Lazy. This is designed for @lazy, and when you use <Lazy> component, you may not need it.

loaderComponent

Type: string Default: div

laoderProps

Type: string Default: {}

loaderComponent and loaderProps is used to create a LoaderComponent when status is unload or loaded.

The result of render(status, props) will be passed to LoaderComponent as children.

onError()

onLoaded()

onLoading()

onUnload()

API: @lazy

Usage:

@routerHooks({
  fetch: async () => {
    await fetchData();
  },
  defer: async () => {
    await fetchDeferredData();
  },
})
@lazy({
  render: (status, props, Component) => {
    if (status === 'unload') {
      return <div style={{ height: 720 }}>Unload</div>;
    } else if (status === 'loading') {
      return <div style={{ height: 720 }}>Loading</div>;
    } else {
      return <Component {...props} />;
    }
  },
  onLoaded: () => console.log('look ma I have been lazyloaded!')
})
class MyComponent extends React.Component {
  render() {
    return (
      <div>
        <img src='http://apod.nasa.gov/apod/image/1502/HDR_MVMQ20Feb2015ouellet1024.jpg' />
      </div>
    );
  }
}

Or

class MyComponent extends React.Component {
  render() {
    return (
      <div>
        <img src='http://apod.nasa.gov/apod/image/1502/HDR_MVMQ20Feb2015ouellet1024.jpg' />
      </div>
    );
  }
}
const myComponent = lazy({
  render: (status, props, Component) => {
    if (status === 'unload') {
      return <div style={{ height: 720 }}>Unload</div>;
    } else if (status === 'loading') {
      return <div style={{ height: 720 }}>Loading</div>;
    } else {
      return <Component {...props} />;
    }
  },
  onLoaded: () => console.log('look ma I have been lazyloaded!')
})(MyComponent);

options

getComponent

With webpack 2 import()

const myComponent = lazy({
  render: (status, props, Component) => {
    if (status === 'unload') {
      return <div style={{ height: 720 }}>Unload</div>;
    } else if (status === 'loading') {
      return <div style={{ height: 720 }}>Loading</div>;
    } else {
      return <Component {...props} />;
    }
  },
  onLoaded: () => console.log('look ma I have been lazyloaded!'),
  getComponent: () => import('./MyComponent'),
})();

API: LazyProvider

You can optionally use LazyProvider and pass a version (such as location) to the value prop. All of the Lazy instances will be reset when version changed.

Example:

class Application extends React.Component {
  render() {
    // when pathname changed, all of the Lazy instances will be reset.
    const { pathname, children } = this.state;
    <LazyProvider value={pathname}>
      { children }
    </LazyProvider>
  }
}

LICENSE

MIT