// -> prev: 获取上一个哥哥元素节点
    // -> 首先获取当前元素的上一个哥哥元素，判断是否为元素节点，不是的话基于当前的继续找到上面的哥哥节点..
    //    直到找到哥哥元素节点为止，如果没有哥哥元素节点，则返回null
    function prev(curEle) {
        if (flag) {
            return curEle.previousElementSibling;
        }
        var pre = curEle.previousSibling;
        while (pre && pre.nodeType !== 1) {
            pre = pre.previousSibling;
        }
        return pre;
    }

    // -> next: 获取下一个弟弟元素节点
    function next(curEle) {
        if (flag) {
            return curEle.nextElementSibling;
        }
        var nex = curEle.nextSibling;
        while (nex && nex.nodeType !== 1) {
            nex = nex.nextSibling;
        }
        return nex;
    }

    // -> prevAll: 获取所有的哥哥元素节点
    function prevAll(curEle) {
        var ary = [];
        var pre = this.prev(curEle);
        while (pre) {
            ary.unshift(pre);
            pre = this.prev(pre);
        }
        return ary;
    }

    // -> nextAll: 获取所有的弟弟节点
    function nextAll(curEle) {
        var ary = [];
        var nex = this.next(curEle);
        while (nex) {
            ary.push(nex);
            nex = this.next(nex);
        }
        return ary;
    }

    // -> sibling: 获取相邻的两个元素节点
    function sibling(curEle) {
        var pre = this.prev(curEle);
        var nex = this.next(curEle);
        var ary = [];
        pre ? ary.push(pre) : null;
        nex ? ary.push(nex) : null;

        return ary;
    }

    // -> siblings: 获取所有的兄弟元素节点
    function siblings(curEle) {
        return this.prevAll(curEle).concat(this.nextAll(curEle));
    }

    // -> index: 获取当前元素的索引
    function index(curElem) {
        return this.prevAll(curElem).length;
    }

    // -> firstChild: 获取第一个元素子节点
    function firstChild(curElem) {
        var childrenNodes = this.children(curElem);
        return childrenNodes.length > 0 ? childrenNodes[0] : null;
    }

    // -> lastChild: 获取最后一个元素子节点
    function lastChild(curElem) {
        var childrenNodes = this.children(curElem);
        return childrenNodes.length > 0 ? childrenNodes[childrenNodes.length - 1] : null;
    }