Insersection Observer API

intersect.js

( function() {
  if( ( "undefined" !== typeof window.orientation ) || ( -1 !== navigator.userAgent.indexOf( "IEMobile" ) ) ) {
    window.addEventListener( "load", function() {
      var elements = document.querySelectorAll( ".people-item" );
      var observer = new IntersectionObserver( function( entries ) {
        entries.forEach( function( entry ) {
          if( entry.isIntersecting ) {
            entry.target.classList.add( "intersecting" );
          }
          else {
            entry.target.classList.remove( "intersecting" );
          }
        } );
      }, { threshold: [ 1.0 ] } );
      document.querySelectorAll( ".people-item" ).forEach( function( element ) {
        observer.observe( element );
      } );
    } );
  }
} )();