Thank you for talking slowly and clearly in this video. Other Google tutorials go so fast for some reason! Great job. I wish there were other API-specific Google channels to apply this same method of teaching and help users get a hang of the basics.
The example page you reference above, "adding a Google Map", that has this video on it, is broken. The marker is not displaying. It doesn't work on your page, in the JSFiddle, or locally on my test site.
We always try to provide a documentation link in the video description. Here are two: Adding a Google Map → goo.gle/36nRIcS Reference documentation → goo.gle/3227Op4
Error: Access to script at 'file://......./index.js' from origin 'null' has been blocked by CORS policy: Cross origin requests are only supported for protocol schemes: http, data, isolated-app, chrome-extension, chrome, https, chrome-untrusted.
The Maps JS API's Geometry Library has spherical.computeDistanceBetween: developers.google.com/maps/documentation/javascript/reference/geometry#spherical.computeDistanceBetween You can manually do it using the Haversine formula: stackoverflow.com/questions/1502590/calculate-distance-between-two-points-in-google-maps-v3
