What is the price offer for ESLint's “consistent return” rule?

Question

What value always returns a value ("undefined") for functions, do you need to explicitly return something?

Why is this rule and what mistakes catch it?

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You can read about the ESLint “consistent return” rule here (says “what”, not “why”).

You can read a speculative analysis of why javascript functions implicitly return undefined here when the stack overflows.

Answer 1

Some languages ​​distinguish between functions and procedures. This does not apply to C-alikes, but it is still a good idea to develop routines in this way.

Linter does not want you to "always return something." It just tells you that if you create a function (as opposed to a procedure), it should return something meaningful anyway (ideally, all the return values ​​should be of the same type).

Example:

function is_visible(object) 

is a function, it must return a value (in this case, Boolean) and can be used in expressions. On the other hand

 function make_visible(object) 

- this is a procedure, it should not return anything and cannot be used in expressions - it is always a statement.

Such a design (and the warning about the linger associated with it) helps a lot to prevent such errors (taken from some random web page):