There is nothing that says "the standard is longitude,latitude". If you want to be picky, most implementations say "easting,northing" and in a geographic coordinate system (e.g. EPSG:4326) that means longitude,latitude. There are so many "standard" coordinate systems out there (see https://github.com/mbostock/d3/wiki/Geo-Projections and http://spatialreference.org/) and many times the units are different (e.g meters, feet, etc using a cartesian coordinate system).
To be fair, if you look at most geo APIs (e.g. GMaps) and you just blindly copy values around without paying attention, you are more likely to be right if you were copying [y,x]. Mind you I say most and not all, since there are very popular geo libraries (e.g. Leaflet) that use [x,y] instead.
I would just pick something, make sure it is well documented and clear and just go with that.
To be fair, if you look at most geo APIs (e.g. GMaps) and you just blindly copy values around without paying attention, you are more likely to be right if you were copying [y,x]. Mind you I say most and not all, since there are very popular geo libraries (e.g. Leaflet) that use [x,y] instead.
I would just pick something, make sure it is well documented and clear and just go with that.