Issue 12 Allow `center` to be an Object

This PR extends circleToPolygon so the function accepts center coordinate either as an array or as an object. Behavior is unchanged when the center coordinate is an array.

Key-pair priorization

Passing the lat and lon values in an object causes the complication that the object can contain more than two keys, and some of the keys might seem to be duplicates (eg: { lat, latitude, longitude }, where lat does not mean "latitude").

This problem can be solved in several ways. I chose to solve it by looking for complete key-pairs. The first found complete key-par is being used (no matter if the keys has the correct values or not). Key pairs are being looked for in the following order:

{ lat: latValue, lon: lonValue }
{ lat: latValue, lng: lonValue }
{ latitude: latValue, longitude: lonValue }

In other words;

the object { lat: 0, latitude: 1, lng: 3, lon: 4, longitude: 5 } will be interpreted as [4, 0]
the object: { lat: 6, latitude: 7, lng: 8, longitude: 9 } will be interpreted as [8, 6]
the object { lat: 10, latitude: 11, longitude 12 } will be interpreted as [12, 11]
the object { lat: "there", latitude: 1, lng: 3, lon: "hello", longitude: 5 } will be interpreted as ["hello", "there"]

Error handling

No valid key pairs

circleToPolygon will throw an error if no complete key pairs are found (when center argument is an object).

In other words, the following key pairs will throw an error:

{ lat, longitude}
{ lng, latitude }
{ log, latitude }

No valid values

An error will be thrown if the first found complete key pair does not have the correct type or values. For example: { lat: "General" lon: "Kenobi", latitude: 120.827492, longitude: 40.729362 } will throw an error since lat/lon is used instead of latitude/longitude

Other

I have chose to accept objects such as { lat, latitude, longitude } since maybe it makes sense for someone to have the key lat in the center object for use somewhere else, idk...

I'm wondering if it makes more sense to prioritize the keys pair latitude/longitude the highest, instead of lowest...

Also, should I have it look for the first valid key-pair instead of the first complete key pair?

I'm open to changing this behavior is requested.

This closes #12 .

gabzim / circle-to-polygon