Sounds like a silly thing, but sometimes you want optional false parameters. If for nothing else than to make your parameters human readable, not just syntactically convenient.

So let’s start out:

var config = {
  //blur: false
};

!config.blur //Oh noes reports true

The trick here is to detect whether the variable is undefined, then for it’s truthy value. Fixed implementation:

  if( !config.blur === false ){
  //Won't execute
  }
  config.blur = false;

  if( config.blur === false ){
  //Will execute
  }

Pretty cool huh? Test with if/else structures or you will get errors.

Update: Thanks Toby for that one