Responsive YouTube embed for WordPress

responsive-YouTube-embed.js

( function( $ ) {
  'use strict';
  
  // We'll assume that the post content (and the video) will be inside a wrapper with class .post-content
  // and the video aspect ratio is 16:9
  
  $( window ).on( 'load resize', function() {
    
    // Take the width of the wrapper
    var contentWidth = $( '.post-content' ).width();
    
    // Resize all YouTube iframes according to the wrapper size with 16:9 aspect ratio
    $( '.post-content iframe[src*="https://www.youtube.com"]' ).each( function() {
        $( this ).width( contentWidth );
        $( this ).height( contentWidth * 9 / 16 );
    } );
  } );
  
} ) ( jQuery );