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"}]}]