How to group complex JSON object by nested properties

How to group complex JSON object by nested properties?

Source: StackOverflow.com

Question

There are points on a map by parsing through a dynamically created GeoJSON file. I'd like to group these points by it's category attribute (each point has a category property). What I'd prefer to do is to parse through each point (already doing that part), and do a check to see if a group for category X exists, and either add the point to that group or make a group and add the point. This would allow me to turn all points of a certain category on/off at once.

An example GeoJSON point:

{
    "crs": null,
    "type": "FeatureCollection",
    "features": [
        {
            "geometry": {
                "type": "Point",
                "coordinates": [
                    -122.382626,
                    47.6657641
                ]
            },
            "type": "Feature",
            "id": 18,
            "properties": {
                "event_set__all": [
                    {
                        "category__category": "Live",
                        "title": "the Tallboys",
                        "cost": "$5",
                        "description": "",
                        "slug": "the-tallboys"
                    }
                ],
                "neighborhood__slug": "ballard",
                "venue": "Tractor Tavern",
                "neighborhood__neighborhood": "Ballard",
                "address": "5213 Ballard Ave NW, Seattle, WA 98107, USA",
                "slug": "tractor-tavern"
            }
        }
    ]
}

The attribute to be used to group each point is e.properties.event_set__all[0].category__category.

Answer

You can group all points with AlaSQL library:

var res = alasql('SELECT features->0->properties->event_set__all->0->category__category \
                      AS category, ARRAY(_) AS points FROM ? GROUP BY category',[data]);

It groups all points with category selected from this long point name like:

[
    {category:"Live1", points: [{point},{point},...] },
    {category:"Live2", points: [{point},{point},...] }
]

Try this example at jsFiddle