[slipwalker]

are you using the mapkit-js[1] to integrate with other platforms than ios, or something else ?

[1]https://developer.apple.com/documentation/mapkitjs

[tailspin2019]

Yep MapKit JS for "find your nearest location" type functionality on a corporate website (with zip/post code lookup, location details overlaid etc.)

Rereading OP I realise the question was about APIs rather than necessarily web-based mapping (which is how I initially had read it)