Construct hierarchy tree from flat list with parent field? [duplicate]

Answer 1

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) {
            if (lookup[obj[parentAttr]] !== undefined) {
                lookup[obj[parentAttr]][childrenAttr].push(obj);
            } else {
                 //console.log('Missing Parent Data: ' + obj[parentAttr]);
                 treeList.push(obj);
            }               
        } else {
            treeList.push(obj);
        }
    });
    return treeList;
};

Fiddle