// integers, decimals, both positive and negative                    
pattern = @"^[+-]?\d+\.?\d*$";

// letters only
pattern = @"^[a-zA-Z].*$";

// characters only
pattern = @"^[a-zA-Z]*$";

// symbols only - space not allowed
pattern = @"^\W[^\s]*$";

// complex email regex
pattern = @"^[\w\.]*@\w*\.\w*\.?(\w*)?$";

// date regex
pattern = @"\d+\d?[/\-_\s]\d+\d?[/\-_\s]\d+";

// JAVASCRIPT // 
ver fileExtensionPattern = /\.([0-9a-z]+)(?=[?#])|(\.)(?:[\w]+)$/gmi;