How to query Firebase for keys that match a string prefix

Question

Since firebase not support any spatial indexing then I use geohash which someone advice here. Geohash is using characters to find the nearby.

So let say I have w2

Answer 1

You can use a normal startAt query to find keys near the specified key. For example, in this case you'd:

var query = firebaseRef.child("geohash").startAt(null, 'c').limit(5);
query.on("child_added", ...);

This will give you the 5 elements after geoHashLatLng when sorted lexigraphically.

If you want to end your query at some specified key, you can do that as well. For example:

var query = firebaseRef.child("geohash").startAt(null, 'c').endAt('d');