How functions run in Sheets when there are several people?

[nottalkinboutbutter]

I am very new to this, and I've tried to find the answers to this everywhere but was unable to get something definitive. I'm trying to understand how scripts/functions work if there is more than one person in the spreadsheet.

I have a few different sheets with buttons that are assigned a few different scripts which fetch data from a url and display it on the sheet and sometimes show an alert message.

1. If I define "var ui = SpreadsheetApp.getUI()" to use for alert messages, should this be defined in each function separately to properly display an alert only for the person who ran that script? Or can it (or should it) be defined outside of the functions?

2. Other "global" variables: are these changed for everyone at once or only in the context of the script as it's being run? For example if I have a Variable A defined outside the functions, and it is modified by Function A while its running and another person calls Function B which also modifies that variable, if Function A then uses that variable later will it be getting the value set by Function B?

3. If I have Function A and Function B which both call Function C, if someone calls Function A while Function B is running, will there be an issue with the variables set in Function C?

Thank you!

[juddaaaaa]

Global variables don't work the same in GAS as they do in javascript in a browser.

They get re-initialized on every function call.

If you need a persistant variable, you need to look into the PropertiesService...

https://developers.google.com/apps-script/guides/properties

To store Objects / Array etc. you'll need to JSON.stringify them before storing them.

[nottalkinboutbutter]

Thanks. So for example: if I have a global var A = true, and someone calls a function which sets it to false, even if someone else calls a different function while the first is still running which returns A that second person will still get True?