Here's a plain Javascript way of doing toggle:
<script>
var toggle = function() {
var mydiv = document.getElementById('newpost');
if (mydiv.style.display === 'block' || mydiv.style.display === '')
mydiv.style.display = 'none';
else
mydiv.style.display = 'block'
}
</script>
<div id="newpost">asdf</div>
<input type="button" value="btn" onclick="toggle();">