css height transition onClick :active

I want to make a button and a div that when I click on the button, t开发者_运维知识库he div appears sliding down. When I click on the button again, the div disappears sliding up.

I know how to do it for 1 element but since there's two involved I am a little lost.

Edit: No Jquery because this is for a mobile web and it can't handle it.

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The way to do this is to set the onClick method in js to change the class of your div.

In CSS, use this

#savemenu {-webkit-transition: height .25s}
.mobmenu.dropup {height: 0; overflow: hidden; border: none;}
.mobmenu.dropdown {height: 50px;}