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//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;
	}