The original algorithm[1] comes from people working at a French university. In France we put the currency directly after the amount, without space : 1€.

[1]: https://gery.casiez.net/1euro/

Euro sign can be used before the amount, depending on the language and local norms, although I’ve seen it mostly after, separated by a space (150 €).

In English the currency symbol is typically before the number, whereas especially in Europe (with exceptions e.g. Switzerland) it is typically after the number. The title here is kind of correct in English I'd say, but the author is Dutch who happens to write in English.

It was moderated I think, the year 2020 was added as well.