dom封装函数

//封装函数，返回元素e的第n层祖先元素节点
function retParent(elem. n) {
while(elem && n) {
elem = elem.parentElement;
n --;
}
return elem;
}
var i = document.getElementsByTagName('i')[0];

//编辑函数，封装myChildren功能，解决以前部分浏览器的兼容性问题
Element.prototype.myChildren = function() {
var child = this.childNodes;
var len = child.length;
var arr = [];
for(var i =0; i < len; i ++){
if(child[i].nodeType == 1) {
arr.push(child[i])
}
}
return arr
}

//自己封装hasChildren()方法，不可用children属性
Element.prototype.myChildren = function() {
var child = this.childNodes;
var len = child.length;
var arr = []
for(var i = 0; i < len; i ++) {
if( child[i].nodeType == 1 ) {
return true
}
}
return false
}

//封装函数，返回元素e的第n个兄弟元素节点，n为正，返回后面的兄弟元素节点，n为负，返回前面的，n为0，返回自己
function retSibling(e,n) {
while(e && n) {
if(n > 0) {
if(e.nextElementSibling) {
e = e.nextElementSibling;
}else{
for(e = e.nextSibling; e.nodeType != 1; e = e = e.nextSibling);
}
n --
}else{
if(e.previousElementSibling) {
e = e.previousElementSibling;
}else{
for(e = e.previousSibling;e.nodeType != 1;e = e.previousSibling);
}
n ++;
}
}
return e;
}