Page loaded below waypoint

Is there a way to detect if the page has been loaded below a waypoint? Basically let’s say you have a waypoint that you reach as you scroll down. This triggers onEnter and onLeave, however if you have a page where you start below the waypoint, these won’t get triggered. Is there a way to detect the current scroll position relative to the waypoint?

[threehams]

componentDidMount solutions leave a window of time (1/3 to 1/2 second in my testing) between the component mount and Waypoint’s resize handlers. If someone scrolls during that time, your app state will still be out of sync.

Although onLeave doesn’t get called on initial render, onPositionChange does. As a workaround, you can take advantage of that. This code causes onEnter and onLeave to mirror each other, and avoids fighting with the setTimeout inside react-waypoint.

import ReactWaypoint from "react-waypoint";

class Waypoint extends Component {
  render() {
    const { onLeave, onPositionChange } = this.props;
    return (
      <ReactWaypoint
        {...this.props}
        onPositionChange={position => {
          // In the case where the page is already scrolled down at the point when
          // the waypoint initializes, handle a "no previous, current above/below" by
          // calling onLeave with the position.
          //
          // See: https://github.com/brigade/react-waypoint/issues/253
          if (
            typeof position.previousPosition === "undefined" &&
            position.currentPosition !== ReactWaypoint.inside &&
            onLeave
          ) {
            return onLeave(position);
          }
          onPositionChange && onPositionChange(position);
        }}
        onLeave={onLeave}
      />
    );
  }
}

[trotzig]

@dzucconi I traced that log down to this test case: https://github.com/brigade/react-waypoint/blob/68d1948b26509941ec601057d1df989bb68366de/test/waypoint_test.jsx#L874

I’ve pushed a PR addressing the confusion around the error message here: https://github.com/brigade/react-waypoint/pull/255. You can safely ignore the error log.