Technique SCR30 uses outdated JavaScript, doesn’t work in browsers

I got an email in German about an issue with SCR30: The example isn’t working as the JavaScript has an error.

Using the `for each (… in …)` is [deprecated in JavaScript](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for_each...in?redirectlocale=en-US&redirectslug=JavaScript%2FReference%2FStatements%2Ffor_each...in), and it looks like browsers have problems interpreting it. If we switch to `for (… of …)` it works like a charm in my browser (Firefox).