Arranging an array of flat paths into a JSON tree like structure

I recently worked on a project where I was required to take an array of flat paths separated by slashes and arrange them into a JSON object in order to display them in a tree from the front end. To be clear, the paths that I was provided looked something like this. The following example utilizes lodash, but could also be accomplished with Array.prototype.forEach(). I, unfortunately, had to support IE8.

“Flat Paths” example:

/FolderA/FolderB/FolderC/Item1
/FolderA/FolderB/Item1
/FolderB/FolderD/FolderE/Item1
/FolderB/FolderD/FolderE/Item2
/FolderA/FolderF/Item1
/ItemInRoot

Given this list of paths, I came up with the following solution. First we will organize our list of paths into an array, like so.

var paths = [
    '/FolderA/FolderB/FolderC/Item1',
    '/FolderA/FolderB/Item1',
    '/FolderB/FolderD/FolderE/Item1',
    '/FolderB/FolderD/FolderE/Item2',
    '/FolderA/FolderF/Item1',
    '/ItemInRoot'
];

Once we have our paths in an array, we then need to set up the function that will process this array.

function arrangeIntoTree(paths, cb) {
    var tree = [];

    // This example uses the underscore.js library.
    _.each(paths, function(path) {

        var pathParts = path.split('/');
        pathParts.shift(); // Remove first blank element from the parts array.

        var currentLevel = tree; // initialize currentLevel to root

        _.each(pathParts, function(part) {

            // check to see if the path already exists.
            var existingPath = _.findWhere(currentLevel, {
                name: part
            });

            if (existingPath) {
                // The path to this item was already in the tree, so don't add it again.
                // Set the current level to this path's children
                currentLevel = existingPath.children;
            } else {
                var newPart = {
                    name: part,
                    children: [],
                }

                currentLevel.push(newPart);
                currentLevel = newPart.children;
            }
        });
    });

    cb(tree);
}

Now that we’ve implemented our function for arranging items into a tree, we can now consume it.

arrangeIntoTree(paths, function(tree) {
    console.log('tree: ', tree);
});

Upon invoking our method, we should see something similar to the following in our console.