from array to nested

gistfile1

$(function() {

    var placeArray = function(array, target) {
        array.forEach(function(item) {
            target = placeObj(item, target);
        });
        return target;
    };

    var placeObj = function(obj, target) {
            if (target.length === 0 ) {
                return;
            }
            for (var i = 0; i < target.length; i++) {
                if (obj.parentId == target[i].id) {
                    target[i].children.push({
                        id: obj.id,
                        children: []
                    });
                    break;
                }
                else {
                    target.forEach(function(t) {
                        placeObj(obj, t.children);
                    });
                }
            }
        return target;
    };
    console.log(placeObj({id:2,parentId:1}, [{id:0,children:[{id:1, children:[]}]}]));
    console.log(placeArray([{id:2,parentId:1}, {id:3, parentId:2}, {id:4, parentId:2}], [{id:0,children:[{id:1, children:[]}]}]));

});