pId的数据结构转children 数据结构(JS)；

在工作中经常遇到需要把带有pId的的list数据转换为children格式的树形结构，一直都
没有找到太好的工具函数。偶然间看到了这个函数，研究了下，感觉这个函数很强大，所以
记录下来,作为备用，同时也贴出来，供大家使用;

/**
 * json格式转树状结构
 * @param   {json}      json数据
 * @param   {String}    id的字符串
 * @param   {String}    父id的字符串
 * @param   {String}    children的字符串
 * @return  {Array}     数组
 */
function transData(a, idStr, pidStr, chindrenStr){
    var r = [], hash = {}, id = idStr, pid = pidStr, children = chindrenStr, i = 0, j = 0, len = a.length;
    for(; i < len; i++){
        hash[a[i][id]] = a[i];
    }
    for(; j < len; j++){
        var aVal = a[j], hashVP = hash[aVal[pid]];
        if(hashVP){
            !hashVP[children] && (hashVP[children] = []);
            hashVP[children].push(aVal);
        }else{
            r.push(aVal);
        }
    }
    return r;
}  

var jsonData = eval('[{"id":"4","pid":"1","name":"大家电"},{"id":"5","pid":"1","name":"生活电器"},{"id":"1","pid":"0","name":"家用电器"},{"id":"2","pid":"0","name":"服饰"},{"id":"3","pid":"0","name":"化妆"},{"id":"7","pid":"4","name":"空调"},{"id":"8","pid":"4","name":"冰箱"},{"id":"9","pid":"4","name":"洗衣机"},{"id":"10","pid":"4","name":"热水器"},{"id":"11","pid":"3","name":"面部护理"},{"id":"12","pid":"3","name":"口腔护理"},{"id":"13","pid":"2","name":"男装"},{"id":"14","pid":"2","name":"女装"},{"id":"15","pid":"7","name":"海尔空调"},{"id":"16","pid":"7","name":"美的空调"},{"id":"19","pid":"5","name":"加湿器"},{"id":"20","pid":"5","name":"电熨斗"}]');  

var jsonDataTree = transData(jsonData, 'id', 'pid', 'chindren');
console.log(jsonDataTree);
//[{"id":"1","pid":"0","name":"家用电器","chindren":[{"id":"4","pid":"1","name":"大家电","chindren":[{"id":"7","pid":"4","name":"空调","chindren":[{"id":"15","pid":"7","name":"海尔空调"},{"id":"16","pid":"7","name":"美的空调"}]},{"id":"8","pid":"4","name":"冰箱"},{"id":"9","pid":"4","name":"洗衣机"},{"id":"10","pid":"4","name":"热水器"}]},{"id":"5","pid":"1","name":"生活电器","chindren":[{"id":"19","pid":"5","name":"加湿器"},{"id":"20","pid":"5","name":"电熨斗"}]}]},{"id":"2","pid":"0","name":"服饰","chindren":[{"id":"13","pid":"2","name":"男装"},{"id":"14","pid":"2","name":"女装"}]},{"id":"3","pid":"0","name":"化妆","chindren":[{"id":"11","pid":"3","name":"面部护理"},{"id":"12","pid":"3","name":"口腔护理"}]}]