Hey Fil, is there a use case for a custom children accessor when working with Maps?

I don't have one in mind but if you need to create one you can use the mapChildren function (which is used internally) as a template : d3.hierarchy(group, function mapChildren(d) { return Array.isArray(d) ? d[1] : null; })

Thanks! I can't see one either and I'm wondering if it's an unnecessary vulnerability. If the accessor returns an iterable it appears to crash (try d => d or d => "anything"). I can open an issue if you think it's warranted. Feel free to remove these comments 🙃

if the children accessor always returns children then you get an infinite loop, which crashes the browser as expected ;) At some point you need to stop the chain. Here's a fun example: d3.hierarchy("root", d => { const n = d3.randomBinomial(30, 1 / d.length)(); if (n) return new Array(n).fill(`child of ${d}`); })