Checking for an Existing, Nonempty String

1.6.checking_for_an_existing_non_empty_string.js

//Use a combination of the typeof operator, the valueof method (shared by all objects) and the length property of String objects

// true if variable exists, is a string, and has a length greater than zero
if ((
  (typeof unkownVariable != "undefined") 
   && (typeof unknownVariable.valueOf() == "string")
   && (unknownVariable.length > 0)
   )) {
  
}

// typeof may return: "number", "string", "boolean", "function", "object", or "undefined"