Support preclustering filtering

[lucaswoj]

Allow users to filter features before they are clustered.

cc @lyzidiamond @mourner

[mourner]

I don't think this should be done on the supercluster side — you can just do geojson.features.filter(function () { ... }) before passing the result to supercluster. If we need this on the GL JS side, let's open a ticket there.

[lucaswoj]

Agreed. Bringing in feature-filter as a dep of supercluster doesn't make much sense. I opened an upstream ticket.

[strech345]

so how does it the filtering for clusters from geojson works?
Please give a example

I need to filter dynamiclally (on user interactions). so it would be nice to use the standard filter functionality in mapbox

[Nogginboink]

I'm not a Javascript expert, but I'm curious about the ramifications of filtering geoJSON points before passing the result to supercluster.

Let's say I want my user to be able to filter results in the GUI. If I have to filter before passing the results to SC, does that mean I need to keep two copies of my data? I'd need to keep one copy of the full dataset (so that I can apply filters to it each time the user changes filtering criteria), and then a second copy of just the filtered data that I pass to supercluster. For a dataset of hundreds of thousands or millions of points, that's a lot of memory spent on two copies of data, isn't it?

If supercluster did the filtering internally with a filter() property, then only one copy of the data would have to be kept in memory. (Although clusters would of course have to be recomputed when filters are applied.)

I may be misunderstanding how Javascript manages memory in this scenario. If I am, I apologize.