Restore fullscreen button on embedded YouTube videos (Chrome Extension)

content.js

var checkDocument = function( doc )
{
	var frames = doc.getElementsByTagName( "iframe" );
	for( var i = 0, l = frames.length; i < l; i++ )
		checkIframe( frames[i] );
};

var checkIframe = function(iframe)
{
	if( iframe.src.indexOf( "https://www.youtube" ) == 0 )
	{
		iframe.src = iframe.src.replace( "?fs=0", "" ).replace( "&fs=0", "" ).replace( "?controls=0", "?controls=1" ).replace( "&controls=0", "&controls=1" );
		iframe.setAttribute( "allowfullscreen", "0" );
		
		if( iframe.hasAttribute( "donotallowfullscreen" ) )
			iframe.removeAttribute( "donotallowfullscreen" );
	}
	else if( iframe.hasAttribute( "data-src" ) && iframe.getAttribute( "data-src" ).indexOf( "https://www.youtube" ) == 0 )
	{
		iframe.setAttribute( "data-src", iframe.getAttribute( "data-src" ).replace( "?fs=0", "" ).replace( "&fs=0", "" ).replace( "?controls=0", "?controls=1" ).replace( "&controls=0", "&controls=1" ) );
		iframe.setAttribute( "allowfullscreen", "0" );
		
		if( iframe.hasAttribute( "donotallowfullscreen" ) )
			iframe.removeAttribute( "donotallowfullscreen" );
	}
	else if( iframe.src.indexOf( "https://twitter.com" ) == 0 )
	{
		// Support for YouTube embedded videos on Twitter
		if( iframe.src.indexOf( "cardname=player" ) > 0 )
			iframe.addEventListener( "load", iframeLoaded );
	}
};

var iframeLoaded = function( e )
{
	e.target.removeEventListener( "load", iframeLoaded );	
	checkDocument( e.target.contentDocument || e.target.contentWindow.document );
};

var observerCallback = function( mutationsList, observer ) 
{
	for( var mutation of mutationsList ) 
	{
		if( mutation.type == 'childList' )
		{
			var addedNodes = mutation.addedNodes;
			for( var i = 0; i < addedNodes.length; i++ )
			{
				if( addedNodes[i].nodeName == "IFRAME" )
					checkIframe( addedNodes[i] );
			}
		}
	}
};

checkDocument( document );

var observer = new MutationObserver( observerCallback );
observer.observe( document.body, { childList: true, subtree: true } );

manifest.json

{
  "manifest_version": 2,
 
  "name": "YouTube Fullscreen Button",
  "version": "1.0",
  "description": "Bring back the fullscreen button to embedded YouTube videos",
 
  "content_scripts": [{
    "js": ["content.js"],
    "matches": ["https://*/*", "http://*/*"]
  }]
}

UPDATE: restored the fullscreen button on embedded YT videos on Twitter.

This isn't doing anything.

@ashergz I haven't used this extension in a long while so I can't concur myself but I believe you. Probably this feature's format has changed (i.e. it's no longer "fs=0" or "controls=0"). I am not planning to update this gist soon but thank you for letting future readers know about this issue 🙂)

Speaking of those who stumble here in search of a solution, here's one that actually works: https://greasyfork.org/en/scripts/829-restore-youtube-embed-defaults