Which is better to write the conditional branch, the caller or the caller?

Suppose you have two JavaScript codes:
Except for fine performance, both should get the same output.
The difference is that if the variable isMorning is true, call the function morningGreeting() or the function morningGreeting() always calls and branches within it.

 if(isMorning) morningGreeting();

function morningGreeting(){
  console.log('Good morning!');
}

morningGreeting();

function morningGreeting(){
  if(isMorning) return;
  console.log('Good morning!');
}

In general, which code is better in terms of serviceability and readability?
Some people may say that it doesn't matter as long as the project is unified.
I'd like to hear your opinion.