从带有父字段的平面列表构造层次树？

function treeify(list, idAttr, parentAttr, childrenAttr) {    if (!idAttr) idAttr = 'id';    if (!parentAttr) parentAttr = 'parent';    if (!childrenAttr) childrenAttr = 'children';    var treeList = [];    var lookup = {};    list.forEach(function(obj) {        lookup[obj[idAttr]] = obj;        obj[childrenAttr] = [];    });    list.forEach(function(obj) {        if (obj[parentAttr] != null) { lookup[obj[parentAttr]][childrenAttr].push(obj);        } else { treeList.push(obj);        }    });    return treeList;};

小提琴