I saw a piece of code that stuck me as odd. What does switch(!0) mean in javascript? What are some cases where this technique would be useful to use?

jsTree uses it in a few places but it looks foreign. I'm sure it has a good reason behind it, but can't figure it out.

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Here is a clip of code:

switch(!0) {
    case (!s.data && !s.ajax): throw "Neither data nor ajax settings supplied.";
    case ($.isFunction(s.data)): //...
                                 break;
}

I saw a piece of code that stuck me as odd. What does switch(!0) mean in javascript? What are some cases where this technique would be useful to use?

jsTree uses it in a few places but it looks foreign. I'm sure it has a good reason behind it, but can't figure it out.

http://www.jstree./

Here is a clip of code:

switch(!0) {
    case (!s.data && !s.ajax): throw "Neither data nor ajax settings supplied.";
    case ($.isFunction(s.data)): //...
                                 break;
}

• javascript
• jquery
• jstree

• 2 Someone is trying to obfuscate their code I'd say. This is a hacky way to not use if and if else. – Torsten Walter Commented Aug 10, 2012 at 23:41
• possible duplicate of What does !1 and !0 mean in Javascript? – user1106925 Commented Aug 11, 2012 at 0:00
• 1 Because sensical code is too mainstream. Also, I say we should name these Yoda switches. – Mahn Commented Aug 11, 2012 at 0:13
• @Mahn HA! I am for the new term. +1 the ment if you like the new term "Yoda switches" – MMeah Commented Aug 12, 2012 at 7:35

2 Answers 2

It's paring each of the cases to boolean true.

Elaborating

case (!s.data && !s.ajax)

If !s.data && !s.ajax evaluates to true, then this case will be selected for execution.

switch(true) is the same as switch(!0)

A switch(!0) is simply the same as switch(true).

This pattern:

switch (true) {
  case (condition): do something; break;
  case (condition): do something; break;
  case (condition): do something; break;
}

Works the same as:

if (condition) {
  do something;
} else if (condition) {
  do something;
} else if (condition) {
  do something;
}