is switch(true) {… valid javascript?

Question

I recently came across code where a switch statement seemed reversed with the answer (boolean) in the switch and the expressions in the case. The code ran fine as intended b

Answer 1

The syntax of switch statement is:

SwitchStatement :  
  switch ( Expression ) CaseBlock  
CaseBlock :  
  { CaseClauses(opt) }  
  { CaseClauses(opt) DefaultClause CaseClauses(opt) }  
CaseClauses :  
  CaseClause  
  CaseClauses CaseClause  
CaseClause :  
  case Expression : StatementList(opt)  
DefaultClause :  
  default : StatementList(opt)

No where it says that switch expression or the case expression has to be a number, string, boolean or anything. true is perfectly acceptable as a switch expression and y < 20 is perfectly acceptable as case expression. Keep in mind that comparison between switch expression and case expressions are made using === operator.

In the code you posted, the first true case will be executed until break is encountered or the switch block ends.