setCenter: not a LatLng or LatLngLiteral with finite coordinates code example

Example: setCenter: not a LatLng or LatLngLiteral with finite coordinates: in property lat: not a number

//The error comes because you pass the value as string:
var lat = document.getElementById('lat').value;

//you need to set it as float:
var lat = parseFloat(document.getElementById('lat').value);