bithons

The solution was wrapping my custom javascript code in in:

(function($){
    // your code here.
})(jQuery);

For more information see: Click here

And for more information about proper way loading the Javascript see the this article what helped me with a clear explanation: Click here

I fixed the problem I will explain it later, I set the topic status on resolved so people don’t take the time for a problem that is already solved.

I will edit this message with the explanation.

Thanks for you reply it worked, and the Regenereate Thumbnails is a handy one. And I am using a child-theme now.

I used this code for setting more image size settings, for people who maybe don’t know how to do it.

$sizes = array(
		'post-thumbnail' => array(
			'width'  => 850,
			'height' => 450,
			'crop'   => true
		),
		'slider-thumbnail' => array(
			'width'  => 1204,
			'height' => 900,
			'crop'   => true
		),
		'related-thumbnail' => array(
			'width'  => 210,
			'height' => 180,
			'crop'   => false
		)
	);

	return $sizes;
}