1. const searchCommonParent=(node1,node2)=>{
    2.         if(node1.contains(node2) return node1;
    3.         return searchCommonParent(node1.parentNode,node2);
    4. }

    js contains方法：

    如果A元素包含B元素，则返回true，否则false

    1. <div id="parent">  
    2.   <p>  
    3.     <strong id="child" >本例子会在火狐中会报错。</strong>  
    4.   </p>  
    5. </div>
    1.  var A = document.getElementById('parent'),  
    2.     B = document.getElementById('child');  
    3.     alert(A.contains(B));  //true
    4.     alert(B.contains(A));  //false