[reb]

Assuming I'm not misunderstanding your question, it appears to cover that right above the snippet:

"Why? This ensures that you can't reassign your references (mutation), which can lead to bugs and difficult to comprehend code."

So it's not about working by reference but avoiding inadvertent reassignment and resulting unpredictability.

[orthoganol]

> Assuming I'm not misunderstanding your question

Numbers are not passed by reference.

It's a lazy example, that has the potential to confuse. I would agree with the downvoters I'm being petty, but c'mon... it's the very first thing you read in your JavaScript guide & it's flawed.

[beaner]

You're right.