Question

I have been at this all day, trying to write a recursive function in Javascript to get the sizes. I need some help :/

Basically, my JSON object contains hierarchical categories/subcategories. I’d like to determine the size of each category/subcategory.

Here is a simple demonstration: http://pastehtml.com/view/bkpzzlabs.html

I’d like to take the JSON on the left and get the HTML on the right. Perhaps I’ve just been staring at this computer monitor for too long because for the life of me I can’t figure this out.

Thanks so much for your help.

Answer 1

The right-hand side of your "demonstration" suggests that you don’t just want to recursively count the total number of endpoints (or "leafs") in your JSON; you want to know the recursive size for each category (non-leaf node) in the tree. The key here is that the nodes in between the leafs and the root don’t count.

Update: I updated the function; read below.

Try this:

function parseTree(parent) {
    var hasNonLeafNodes = false;
    var childCount = 0;
    
    for (var child in parent) {
        if (typeof parent[child] === 'object') {
            // Parse this sub-category:
            childCount += parseTree(parent[child]);
            // Set the hasNonLeafNodes flag (used below):
            hasNonLeafNodes = true;
        }
    }
    
    if (hasNonLeafNodes) {
        // Add 'num_children' element and return the recursive result:
        parent.num_children = childCount;
        return childCount;
    } else {
        // This is a leaf item, so return 1:
        return 1;
    }
}

This function will modify the original object, so that a new key 'num_children' is added to each non-leaf node in the tree. The function returns the total number of leaf nodes in all of the parent‘s descendants. Note that it’s also perfectly possible to call this function on a subset of your object.

Here is a live demo: http://jsfiddle.net/PPvG/CXXaB/

Sorry about that! I had to do something else for a bit and, apparently, forgot what it was I was doing here… 😉

The updated solution should count the addresses correctly, but keep in mind that arrays can’t have named keys (such as num_children). This is relevant in your example as e.g. "Pothole" is an array.