var tree = {
            "id": 0,
            "a1": {
                "id": 1,
                "name": "a1",
                "children": {
                    "b1": "b1_1",
                    "b2": "b1_2",
                    "b3": "b1_3"
                }   
            },
            "a2": {
                "id": 1,
                "name": "a2",
                "children": {}
            },
            "a3": {
                "id": 1,
                "name": "a3",
                "children": {
                    "b1": "b3_1",
                    "b2": "b3_2",
                    "b3": "b3_3"
                }
            }
        };

var Tree = function ( module ){
    function createNodeList( obj ) {
        //創(chuàng)建ul節(jié)點和documentFragmeng中間變量
        var n = document.createElement("ul"),
            docfrag = document.createDocumentFragment();

        //判斷obj是根節(jié)點還是孩子節(jié)點
        if(obj.id == 0) {
            n.setAttribute("class", "tree_0");

            for(var key in obj) {
                if(key == "id") continue;
                //將節(jié)點插入
                var c = document.createElement("li"),
                    span = document.createElement("span");
                span.appendChild(document.createTextNode( obj[key].name ));
                c.appendChild(span);
                docfrag.appendChild( c );
            }
        }else if(obj.id && obj.id == 1) {
            n.setAttribute("class", "tree_1");

            for(var key in obj) {
                if(key == "id" || key == "name" || !obj.children) continue;
                for( var item in obj.children){
                    //將節(jié)點插入
                    var c = document.createElement("li");
                    c.appendChild(document.createTextNode( obj.children[item] ));
                    docfrag.appendChild( c );
                }
            }
        }
        n.appendChild( docfrag );
        //返回開始構(gòu)建的ul節(jié)點
        return n;
    }

    //隱藏及顯示 工具函數(shù)
    function toggle(c){
        c.style.display = ((c.style.display == "none") ? "" : "none");
    }

    function createTree( obj ) {
        var root, child, count = 0;

        root = createNodeList( obj );
        for(var key in obj){
            if(obj[key] == "id" || !obj[key].children) continue;
            child = createNodeList(obj[key]);
            root.children[count].appendChild( child );
            //count來判斷插入的位置
            count++;
        }
        return root;
    }

    var T = createTree(module);
    var list = T.children;
    for(var i = 0, len = list.length; i < len; i++){
        list[i].getElementsByTagName("span")[0].onclick = function(){
            var obj = this.nextSibling;
            toggle(obj);
        }
    }
    return T;
}

createNodeList() //適用于構(gòu)建一個樹子節(jié)點

createTree() //構(gòu)建一棵樹

window.onload = function(){
    var T = new Tree(tree);
    document.getElementsByTagName("body")[0].appendChild(T);
}