.a1{margin: 0 auto;width: 200px;height: 200px;border: 1px black solid;}
#b{margin: 20px auto;width: 100px;height: 40px;display: block;}
			

<div id="a" class="a1">测试1 </div>
<button id="b" type="button" >按钮</button>
<div id="c" class="a1">测试2 </div>

		var aaa=document.getElementById("a");
		var ccc=document.getElementById("c");
		var bbb=document.getElementById("b");
		bbb.onclick= function(){
			var abs=1;
			var p;
			if (abs==1) {
				p=aaa.innerHTML
				aaa.innerHTML=ccc.innerHTML
				ccc.innerHTML=p
			} else{
				p=ccc.innerHTML
				ccc.innerHTML
				aaa.innerHTML=p
			}
		}