Question

I have a JSON tree structure:

nodes = 
[
{
    "name": "user1",
    "children": [
        {
            "name": "user2"
        },
        {
            "name": "user3",
            "children": [
                {
                    "name": "user4"
                }
            ]
        },
        {
            "name": "user5"
        }
    ]
}
]

that I would like to convert to a parent-link structure:

[{"name": "user1","parent": "null"},
 {"name": "user2","parent": "user1"},
 {"name": "user3","parent": "user1"},
 {"name": "user4","parent": "user3"},
 {"name": "user5","parent": "user1"}]

I have tried to traverse the tree recursively but without success accessing the parent object:

rebuild(nodes,parentLink);

function parentlink(key,value) {
    var obj = { name: value , parent: ??? };
    if (key == "name"){
        nodes.push(obj);
    }
}

function rebuild(o,func) {
    for (i in o) {
        func.apply(this,[i,o[i]])
      if (typeof(o[i])=="object") {
        traverse(o[i],func,nodes);
      }
    }
}

In developer tools I can see the parent objects for each child, but I don’t know how to access them. What should I do to add the parent to each user?

Answer 1

I’m not gonna lie, I didn’t bother looking at your code – this is how I would do it:

http://jsfiddle.net/J6G2W/1/

function processChildren(item, ret, parent) {
    for (var i = 0; i < item.length; i++) {
        var cur = item[i];
        var cur_name = cur.name;
        ret.push({"user": cur_name, "parent": parent});
        if ("children" in cur && cur.children.length > 0) {
            processChildren(cur.children, ret, cur_name);
        }
    }
}

var all = [];

processChildren(nodes, all, null);

console.log(JSON.stringify(all));

Output is:

[{"user":"user1","parent":null},{"user":"user2","parent":"user1"},{"user":"user3","parent":"user1"},{"user":"user4","parent":"user3"},{"user":"user5","parent":"user1"}]

Which seems to be what you’re looking for. You’re welcome to modify what of my code to work more like yours, I just thought I’d share what I’d do 🙂

UPDATE:

If, for some reason, you want to make it more extendable, you can customize which keys are the “name” and which are the “children”…for example:

http://jsfiddle.net/J6G2W/2/

function startProcess(item, ret, key_look, children_look, parent) {
    function processChildren(item2, ret2, parent2) {
        for (var i = 0; i < item2.length; i++) {
            var cur = item2[i];
            var cur_name = key_look in cur ? cur[key_look] : null;

            ret.push({"user": cur_name, "parent": parent2});
            if (children_look in cur && cur[children_look].length > 0) {
                processChildren(cur[children_look], ret, cur_name);
            }
        }
    }

    processChildren(item, ret, parent);
}

var all = [];

startProcess(nodes, all, "name", "children", null);

console.log(JSON.stringify(all));

Notice how you only have to specify the key_look, children_look arguments once. The inner function can access those parameters while only passing the important things each recursion. This probably isn’t important, I just wanted to figure it out 🙂