Converting flat structure to hierarchical

This is how I would do it:

var flatArray = [{
    Description: "G",
    guid: "c8e63b35",
    parent: null,
}, {
    Description: "Z",
    guid: "b1113b35",
    parent: "c8e63b35",
}, {
    Description: "F",
    guid: "d2cc2233",
    parent: "b1113b35",
}, {
    Description: "L",
    guid: "a24a3b1a",
    parent: null,
}, {
    Description: "K",
    guid: "cd3b11caa",
    parent: "a24a3b1a",
}];

var recursiveArray = unflatten(flatArray);

alert(JSON.stringify(recursiveArray, null, 4));
<script>
function unflatten(items) {
    return items.reduce(insert, {
        res: [],
        map: {}
    }).res;
}

function insert(obj, item) {
    var parent     = item.parent;
    var map        = obj.map;
    map[item.guid] = item;

    if (parent === null) obj.res.push(item);
    else {
        var parentItem = map[parent];

        if (parentItem.hasOwnProperty("Children"))
            parentItem.Children.push(item);
        else parentItem.Children = [item];
    }

    return obj;
}
</script>

Of course, this only works if your flatArray has the property that every parent appears before its children.

Hope that helps.


This one works nicely and is easy to read:

function flatToHierarchy (flat) {

    var roots = [] // things without parent

    // make them accessible by guid on this map
    var all = {}

    flat.forEach(function(item) {
      all[item.guid] = item
    })

    // connect childrens to its parent, and split roots apart
    Object.keys(all).forEach(function (guid) {
        var item = all[guid]
        if (item.parent === null) {
            roots.push(item)
        } else if (item.parent in all) {
            var p = all[item.parent]
            if (!('Children' in p)) {
                p.Children = []
            }
            p.Children.push(item)
        }
    })

    // done!
    return roots
}

Tags:

Javascript

Algorithm

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