Read more on same page?

I want to make it so that when you use “read more” in my posts that it creates a separation but doesn’t make the rest of the post after read more goto another page, I want it directly under what text. One may wonder why the hell would I do this, the reason is I want to use a show/hide javascript and keep everything on the same page. I saw a plugin (called show/hide) but it doesn’t work for the latest version of wordpress so I intend to hack my own, I just don’t know how to manipulate read more, yet. Thanks.