I think it will be .js not .ftd in docs

![image](https://github.com/fastn-stack/fastn.com/assets/113763427/cea8e694-bdea-4003-a49d-6160986b31a9)
**URL**: https://fastn.com/js-in-function/

I think, the code of index.ftd should be looking like:
```
-- ftd.text: Click here to print name in alert!
$on-click$: $call-js-fn(a = FifthTry Alert)

-- void call-js-fn(a):
string a:
js: functions.js ; <hl>

show_alert(a) ; <hl>
```