Why does d3.nest.map prepend a prefix? about d3-collection

[dayvidwhy]

@mbostock if you get a chance would you be able to reply to this?

[mbostock]

http://2ality.com/2012/01/objects-as-maps.html

You should use ES Map instead of Object.

[dayvidwhy]

@mbostock correct me if I'm wrong, but you're asking me to just splice off the $ from the start of the keys?

edit:
I just saw this line;
https://github.com/d3/d3-collection/blame/5aad1d67f264c0b3b6a9f3e9833021497f03beeb/src/map.js#L26
Sorry I wasn't familiar with the new data structure, thanks for the information that's really interesting.

[mbostock]

No, you shouldn’t be iterating over the properties on a d3.map instance, as those are private; you should be using map.keys.