Javascript - Have H1 tag populate title tag

1

I have a question…

I want to dynamically write to the title tags via javascript, and I want it to get text from the already existing H1 tag.

I don’t know javascript but I invision to work like this:

<script>
txt = find.h1 //first <H1> tag on page
javaTitle = (My Homepage ‘-’ + ‘txt’)

ANy ideas?
Any help would be awesome!

Thanks!