onScrollRAF

on-scroll-raf.js

export const onScrollRAF = ( callback ) => {
  let scrollY = window.pageYOffset;
  let lastScrollY = -1;
  let frameRendered = false;

  window.addEventListener( 'scroll', () => {
    scrollY = window.pageYOffset;
    frameRendered = false;
  } );

  window.addEventListener( 'resize', () => {
    frameRendered = false;
  } );

  const tick = () => {
    if ( ! frameRendered ) {
      callback( scrollY, lastScrollY );
      lastScrollY = scrollY;
      frameRendered = true;
    }
    requestAnimationFrame( tick );
  }

  requestAnimationFrame( tick );
}