static public function isString(value):Boolean
Returns value is a string type value. with undefined or null value, false returned.
static public function replace(targetString:String, oldString:String, newString:String):String
replace oldString with newString in targetString
static public function trim(targetString:String):String
remove all the blankspace in targetString
static public function trimLeft(targetString:String):String
remove only the blankspace on targetString's left