Try something like
var arry = [{ "Id": "1", "Name": "abc", "Parent": "", "attr": "abc" },
{ "Id": "2", "Name": "abc", "Parent": "1", "attr": "abc" },
{ "Id": "3", "Name": "abc", "Parent": "2", "attr": "abc" },
{ "Id": "4", "Name": "abc", "Parent": "2", "attr": "abc" }];
function convert(array){
var map = {};
for(var i = 0; i < array.length; i++){
var obj = array[i];
obj.items= [];
map[obj.Id] = obj;
var parent = obj.Parent || '-';
if(!map[parent]){
map[parent] = {
items: []
};
}
map[parent].items.push(obj);
}
return map['-'].items;
}
var r = convert(arry)
Demo: Fiddle
Result
[{
"Id" : "1",
"Name" : "abc",
"Parent" : "",
"attr" : "abc",
"children" : [{
"Id" : "2",
"Name" : "abc",
"Parent" : "1",
"attr" : "abc",
"children" : [{
"Id" : "3",
"Name" : "abc",
"Parent" : "2",
"attr" : "abc",
"children" : []
}, {
"Id" : "4",
"Name" : "abc",
"Parent" : "2",
"attr" : "abc",
"children" : []
}]
}]
}]