How can I make a custom JS function?

Here is an idea of what I’m trying to do – a custom shorthand:

on_cl('#id' /* or .class instead of #id */){
  // insert code here
}

, to not paste this over and over:

document.querySelector('#id' /* or .class */).addEventListener('click', () => {
  // insert code here
})

. Basically, these 2 chunks of code should be equivalent.

How can I do this?

I searched for an answer on MDNdocs, but didn’t find what I wanted.