Just a PSA for Openstreetmap Openlayers 5.3.0 API users.
The rawgit CDN ol.js file appears to contain a malformed ternary operation that causes browsers to not create the ol object, breaking map programs.
The Firefox web console says:
SyntaxError: missing : in conditional expression ol.js:1:34694
The solution is to switch CDN from rawgit to cdn.jsdelivr.net like this:
So definitely test your existing Openlayers code on a current version of Firefox.
There’s only a couple of searchable references starting May, 2020, so it’s something fairly new.