README.md

react-viewport-monitor

This Higher-Order React component enables you to write components that respond to changes in the visible content.

Example

import React from 'react';
import ViewportMonitor from 'viewport-monitor';

const viewportSelector = ({ top }) => ({ viewportEdge: top });

@ViewportMonitor(viewportSelector, 'top')
export default class Fixed extends React.PureComponent {
  render() {
    return (
      <div style={{ position: 'absolute', top: this.props.viewportEdge }}>
        I appear to be `position: fixed`!
      </div>
    );
  }
}

API

ViewportMonitor([selector], [...viewportProps]) => (Component) => WrappedComponent

Subscribes the given Component to changes to the given viewportProps, which it will receive as additional props.

Arguments

• selector(viewport, [ownProps]) => mergeProps – This function generates additional props (to be merged atop the inbound props) from the viewport definition, and will be invoked whenever the viewport is changed. Additionally, this function may also receive the inbound props as a second argument – in this case, selector will additionally be called whenever the incoming props are changed. The return value of this function must be an object. If the selector argument is omitted or falsey, a default implementation will be provided.

• viewportProps – Any number of additional arguments may be provided to explicitly name the viewport properties that the wrapped Component is interested in. The following values have meaning:

  • 'top'
  • 'right'
  • 'bottom'
  • 'left'
  • 'height'
  • 'width'
  • 'any'

  If no properties are named, 'any' is implicitly assumed.

Advantages

• Scroll and resize events are throttled to once per animation frame.
• Only one DOM event subscription per event.

Disadvantages

• Currently only works with ReactDOM.
• Currently only works at the window level.