你这个样例没法写代码，说一说思想。

先按 level 排序

为结果创建一个对象

再维护一个数组，为结果的每一层 list

然后 push 就可以

需要考虑的一个问题，如果中间一个等级不存在如何处理

    var dataJson2= [{"name":"测试2","id":"1","level": "00001"},  //5位数代表1级，10位数代表2级，以此类推
                 {"name":"**a","id":"1","level": "0000100001"},
                 {"name":"***a","id":"1","level":"000010000100001"},
                 {"name":"***a","id":"1","level":"000010000100002"},
                 {"name":"***a","id":"1","level":"000010000100003"},
                 {"name":"**a","id":"1","level": "0000100002"},
                 {"name":"**a","id":"1","level": "0000100003"},
                 {"name":"*b","id":"1","level":  "00002"}]

addTree(dataJson2);
function addTree(treeData) {
    var sortLenght=treeData[0].level.length;
    //排序
    var myArr = [];
        for(var i = 0; i < treeData.length; i++) {
            var thisIndex = treeData[i].level.length / sortLenght - 1;
            if(myArr[thisIndex] === undefined) {
                myArr[thisIndex] = []
            }
            myArr[thisIndex].push(i)
        }

            //组成梯形
    var ladderArr = [];
        for(var i = myArr.length - 1; i >= 0; i--) {
            switch(i) {
                case 0:
                    for(var l = 0; l < myArr[i].length; l++) {
                        ladderArr.push(treeData[myArr[i][l]])
                    }
                    break;
                default:
                    for(var j = 0; j < myArr[i].length; j++) {
                        var str = treeData[myArr[i][j]].level.substr(0, i * sortLenght);
                        for(var k = 0; k < myArr[i - 1].length; k++) {
                            if(treeData[myArr[i - 1][k]].level === str) {
                                if(treeData[myArr[i - 1][k]].list === undefined) treeData[myArr[i - 1][k]].list = [];
                                treeData[myArr[i - 1][k]].list.push(treeData[myArr[i][j]])
                            }
                        }
                    }
            }
        }

    var treeJson=eval(ladderArr);
}

//解决方法如上，代码并非本人所写