取两个HTML节点最近的公共父节点

gistfile1.js

function getCommonParent(el1,el2){

    var parents1 = [];
    var el = el1;
    while(el) {
        parents1.unshift(el);
        el = el.parentNode;
    }

    var parents2 = [];
    var el = el2;
    while(el) {
        parents2.unshift(el);
        el = el.parentNode;
    }

    var i = 0;

    while(i<parents1.length && i<parents2.length && parents1[i+1] == parents2[i+1])
        i++;

    return parents1[i];
}

再来一段使用的标准compareDocumentPosition的，把代码修改得简洁了一点。

function getCommonParent(a,b){
    var c = a.compareDocumentPosition(b);
    if(c & 8){
        return b.parentNode;
    }else if(c & 16){
        return a.parentNode;
    }else if(c & 6){
        while(!(8 & a.compareDocumentPosition(b=b.parentNode)));
        return b;
    }
    return null;
}