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From: Arno Welzel <usenet@arnowelzel.de>
Newsgroups: comp.lang.javascript
Subject: Re: Logical conundrums if () else if()
Date: Mon, 30 Dec 2019 21:35:41 +0100
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Jonas Thörnvall:

> No i am more curious about how two code fragments that work perfectly
> on their own with a "single if" can behave differently when connected
> by an else if, i find that mysterious.

Example:

Assume a<b is true and also x>y is true.

if (a<b && x>y) {
  // will execute, since a<b is true and also x>y is true
}

if (a<b) {
  // will also execute, since a<b is true and no other condition
  // needs to be fulfilled
}

BUT BEWARE:

if (a<b && x>y) {
  // will execute, since a<b is true and also x>y is true
} else if (a<b) {
  // will NOT execute, since the first condition was already met
  // and this code path therefore will never be run
}

So the second fragemnt can also be read as:

if (a<b) {
  if (x>y) {
    // do something if a<b AND x>y
  } else {
    // do something else if a<b
  }
}

HTH

-- 
Arno Welzel
https://arnowelzel.de