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I have a complex json file that I have to handle with javascript to make it hierarchical, in order to later build a tree. Every entry of the json has : id : a unique id, parentId : the id of the parent node (which is 0 if the node is a root of the tree) level : the level of depth in the tree

The json data is already "ordered". I mean that an entry will have above itself a parent node or brother node, and under itself a child node or a brother node.

Input :

{
    "People": [
        {
            "id": "12",
            "parentId": "0",
            "text": "Man",
            "level": "1",
            "children": null
        },
        {
            "id": "6",
            "parentId": "12",
            "text": "Boy",
            "level": "2",
            "children": null
        },
                {
            "id": "7",
            "parentId": "12",
            "text": "Other",
            "level": "2",
            "children": null
        },
        {
            "id": "9",
            "parentId": "0",
            "text": "Woman",
            "level": "1",
            "children": null
        },
        {
            "id": "11",
            "parentId": "9",
            "text": "Girl",
            "level": "2",
            "children": null
        }
    ],
    "Animals": [
        {
            "id": "5",
            "parentId": "0",
            "text": "Dog",
            "level": "1",
            "children": null
        },
        {
            "id": "8",
            "parentId": "5",
            "text": "Puppy",
            "level": "2",
            "children": null
        },
        {
            "id": "10",
            "parentId": "13",
            "text": "Cat",
            "level": "1",
            "children": null
        },
        {
            "id": "14",
            "parentId": "13",
            "text": "Kitten",
            "level": "2",
            "children": null
        },
    ]
}

Expected output : 

{
    "People": [
        {
            "id": "12",
            "parentId": "0",
            "text": "Man",
            "level": "1",
            "children": [
                {
                    "id": "6",
                    "parentId": "12",
                    "text": "Boy",
                    "level": "2",
                    "children": null
                },
                {
                    "id": "7",
                    "parentId": "12",
                    "text": "Other",
                    "level": "2",
                    "children": null
                }   
            ]
        },
        {
            "id": "9",
            "parentId": "0",
            "text": "Woman",
            "level": "1",
            "children":
            {

                "id": "11",
                "parentId": "9",
                "text": "Girl",
                "level": "2",
                "children": null
            }
        }

    ],    

    "Animals": [
        {
            "id": "5",
            "parentId": "0",
            "text": "Dog",
            "level": "1",
            "children": 
                {
                    "id": "8",
                    "parentId": "5",
                    "text": "Puppy",
                    "level": "2",
                    "children": null
                }
        },
        {
            "id": "10",
            "parentId": "13",
            "text": "Cat",
            "level": "1",
            "children": 
            {
                "id": "14",
                "parentId": "13",
                "text": "Kitten",
                "level": "2",
                "children": null
            }
        }

    ]
}
share|improve this question
 
There are several ways to do that, did you try anything yet? –  bfavaretto Aug 2 '13 at 13:23
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1 Answer

up vote 0 down vote accepted

This is fairly easy to do if you keep all the nodes as references.

var nodes = [
    {
        "id": "12",
        "parentId": "0",
        "text": "Man",
        "level": "1",
        "children": null
    }, { /*...*/ } ];

var map = {}, node, roots = [];
for (var i = 0; i < nodes.length; i += 1) {
    node = nodes[i];
    node.children = [];
    map[node.id] = i; // use map to look-up the parents
    if (node.parentId !== "0") {
        nodes[map[node.parentId]].children.push(node);
    } else {
        roots.push(node);
    }
}
console.log(roots); // <-- there's your tree
share|improve this answer
 
keep in mind that with this solution, your nodes must be ordered specifically to make sure the parents are pushed into the map first, otherwise the lookup process will error... so you either need to sort em on the level property, or you need to push them into the map first. and use a separate for loop for the lookup. (i prefer sort however when you don't have a level property the separate loops might be an option) –  Sander Nov 15 '13 at 18:55
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