I'm literally just starting out with learning html, css and js so forgive my newbieness but I'm wondering if it would bepossible to find and change an image on a wp site using js?

To cut a long story short I want to identify the image that's attached to an h1 class and swop it for a different image depending on the h1 text. Would that be possible and anyone able to offer some pointers?

Thanks in advance