Lazyload your Components, Images or anything matters the performance.
- Take performance in mind, only 2 event listeners for all lazy-loaded components
- Support both
one-time lazy loadandcontinuous lazy loadmode scroll/resizeevent handler is throttled so you won't suffer frequent update, you can switch to debounce mode too- Decorator supported
- Server Side Rendering friendly
- Thoroughly tested
2.0.0 is finally out, read Upgrade Guide, it's almost painless to upgrade!
$ npm install --save react-lazyload
import React from 'react';
import ReactDOM from 'react-dom';
import LazyLoad from 'react-lazyload';
import MyComponent from './MyComponent';
const App = () => {
return (
<div className="list">
<LazyLoad height={200}>
<img src="tiger.jpg" /> /*
Lazy loading images is supported out of box,
no extra config needed, set `height` for better
experience
*/
</LazyLoad>
<LazyLoad height={200} once >
/* Once this component is loaded, LazyLoad will
not care about it anymore, set this to `true`
if you're concerned about improving performance */
<MyComponent />
</LazyLoad>
<LazyLoad height={200} offset={100}>
/* This component will be loaded when it's top
edge is 100px from viewport. It's useful to
make user ignorant about lazy load effect. */
<MyComponent />
</LazyLoad>
<LazyLoad>
<MyComponent />
</LazyLoad>
</div>
);
};
ReactDOM.render(<App />, document.body);If you want to have your component lazyloaded by default, try this handy decorator:
import { lazyload } from 'react-lazyload';
@lazyload({
height: 200,
once: true,
offset: 100
})
class MyComponent extends React.Component {
render() {
return <div>this component is lazyloaded by default!</div>;
}
}You should aware that your component will only be mounted when it's visible in viewport, before that a placeholder will be rendered.
So you can safely send request in your component's componentDidMount without worrying about performance loss or add some pretty entering effects, see this demo for more detail.
Type: Number/String Default: undefined
In the first round of render, LazyLoad will render a placeholder for your component if no placeholder is provided and measure if this component is visible. Set height properly will make LazyLoad calculate more precisely. The value can be number or string like '100%'. You can also use css to set the height of the placeholder instead of using height.
Type: Bool Default: false
Once the lazy loaded component is loaded, do not detect scroll/resize event anymore. Useful for images or simple components.
Type: Number/Array(Number) Default: 0
Say if you want to preload a component even if it's 100px below the viewport (user have to scroll 100px more to see this component), you can set offset props to 100. On the other hand, if you want to delay loading a component even if it's top edge has already appeared at viewport, set offset to negative number.
If you provide this props with array like [200, 200], it will set top edge offset and bottom edge offset respectively.
Type: Bool Default: true
Listen and react to scroll event.
Type: Bool Default: false
Respond to resize event, set it to true if you do need LazyLoad listen resize event.
NOTICE If you tend to support legacy IE, set this props carefully, refer to this question for further reading.
Type: Bool Default: false
If lazy loading components inside a overflow container, set this to true. Also make sure a position property other than static has been set to your overflow container.
Type: Bool / Number Default: true
By default, LazyLoad will have all event handlers debounced in 300ms for better performance. You can disable this by setting debounce to false, or change debounce time by setting a number value.
Type: Bool / Number Default: false
If you prefer throttle rather than debounce, you can set this props to true or provide a specific number.
NOTICE Set debounce / throttle to all lazy loaded components unanimously, if you don't, the first occurrence is respected.
Type: Any Default: undefined
Specify a placeholder for your lazy loaded component.
If you provide your own placeholder, do remember add appropriate height or minHeight to your placeholder element for better lazyload performance.
Type: Bool Default: false
The lazy loaded component is unmounted and replaced by the placeholder when it is no longer visible in the viewport.
It is available to manually trigger checking for elements in viewport. Helpful when LazyLoad components enter the viewport without resize or scroll events, e.g. when the components' container was hidden then become visible.
Import forceCheck:
import { forceCheck } from 'react-lazyload';Then call the function:
forceCheck();$ npm run demo:watch
$ npm run build
Let's say there is a fixed date picker on the page, when user picks a different date, all components displaying data should send ajax requests with new date parameter to retreive updated data, even many of them aren't visible in viewport. This makes server load furious when there are too many requests in one time.
Using LazyLoad component will help ease this situation by only updating components visible in viewport.
MIT