[Nexus]

<div>див</div>
<button>кнопка</button>
<script>
//скрипт
var nodes = document.querySelectorAll('div,button'),
    text = [].map.call(nodes, function(node) {
        return node.innerHTML;
    });

[].forEach.call(nodes, function(node, i) {
    node.innerHTML = text[+(!i)];
});
</script>

или

<div>див</div>
<button>кнопка</button>
<script>
//скрипт
var nodes = document.querySelectorAll('div,button'),
    text=nodes[0].innerHTML;

nodes[0].innerHTML=nodes[1].innerHTML;
nodes[1].innerHTML=text;
</script>