Can multiple "d3.js Dendrogram" nodes point to the same leaf node?

Question

I've started a new JavaScript project based on the example at: http://bl.ocks.org/mbostock/4063570

Everything with the d3 Dendrogram is great so far except that my data will probably always contain duplicate leaves (terminal nodes). In my data only the leaves could ever contain duplicate data. All internal nodes (between root and leaves) are strictly distinct well before d3 comes into play.

I could add something to the node(s) name (d.name) to make each node totally unique, but I'd rather 'reuse' leaf nodes and make all internal nodes point to and share a single leaf if possible.

Does anyone out there know how to do this?

Many thanks in advance! Drew Barfield

Answer 1

The D3 data join expects that each DOM node will correspond to a different element in the data array. However, there's nothing stopping 2 elements in the data array from referring to the same underlying object.

It comes down to whether you are OK with the default join key (which is array index) or if you want to achieve a sense of "object permanence" on data update by mapping specific data elements to specific nodes. To have that happen you need to define a custom join key function, which by definition relies on some way to differentiate the data elements.

Personally, I think that if you're doing any amount of data updating involving enter/exit/update, life will be much easier if each data element is unique and has some kind of "id" or "key" property that you can use to identify it. Reusing data elements will likely be more headache than it's worth.

You didn't actually mention what you are trying to achieve by sharing data? Is it just a memory saving optimization or is there another reason? If it's just memory, I wouldn't bother.