Javascript Regular Expressions

RegExp Syntax

var myRegExp = /pattern/[switch]

RegExp Methods

myRegExp.exec(string);  -- executes a search 
myRegExp.test(string);  -- tests if a pattern exists 

var reDigit = /^\d/ 
function validate(str) { 
  if (!reDigit.test(str)) alert("Please use only digits.") 
}

RegExp Patterns

var reWhitespace     = /^\s+$/ 
var reLetter         = /^[a-zA-Z]$/ 
var reAlphabetic     = /^[a-zA-Z]+$/  
var reAlphnumeric    = /^[a-zA-Z0-9]+$/  
var reDigit          = /^\d/  
var reLetterOrDigit  = /^[a-zA-Z]|\d$/ 
var reInteger        = /^\d+/  
var reSignedInteger  = /^(\+|-)?\d+$/ 
var reEmail          = /^+\@.+\..+$/ 

function getNumbers(str) { 
   str = String(str)
   return str.replace(/D/g, "")
}

Summary of RegExp Pattern Syntax

  That's the end. Feel free to cut and paste this code and use it yourself. Thanks for reading and feel free to jump around Wise ASP using the select box at the top of the screen.

Recommended Links

Softpanorama Recommended

Top articles

Sites

• MIND : Validation made simple with Javascript Regular Expressions
• Book : Instant Javascript
• Character Matching (Scripting)

• Regular Expressions

  Introduction to Regular Expressions Microsoft guide to Jscript regular expressions see also Microsoft Windows SDK

  The information contained in these pages is intended to provide a introduction to regular expressions in general.

  While an attempt has been made to make each topic stand on it's own, much of the information contained in these topics relies upon the understanding of a previously introduced feature or concept. Therefore, it's recommended that you peruse these topics sequentially for the best overall understanding of the material.

  The Introduction to Regular Expressions consists of the following individuals topics:

  • Regular Expressions
  • Early Beginnings
  • Uses for Regular Expressions
  • Regular Expression Syntax
  • Build a Regular Expression
  • Order of Precedence
  • Ordinary Characters
  • Special Characters
  • Non-Printable Characters
  • Character Matching
  • Quantifiers
  • Anchors
  • Alternation and Grouping
  • Backreferences

  RegExp Object

  An intrinsic global object that stores information about the results of regular expression pattern matches.

  RegExp.property

  The required property argument can be any one of the RegExp object properties.

  Remarks

  The RegExp object cannot be created directly, but is always available for use. Until a successful regular expression search has been completed, the initial values of the various properties of the RegExp object are as follows:

  Property	Shorthand	Initial Value
  index		-1
  lastIndex		-1
  lastMatch	$&	Empty string.
  lastParen	$+	Empty string.
  leftContext		Empty string.
  rightContext		Empty string.
  $1 - $9	$1 - $9	Empty string.

  
  Its properties have undefined as their value until a successful regular expression search has been completed.

  The global RegExp object should not be confused with the Regular Expression object. Even though they sound like the same thing, they are separate and distinct. The properties of the global RegExp object contain continually updated information about each match as it occurs, while the properties of the Regular Expression object contain only information about the matches that occur with that instance of the Regular Expression.

  Example

  The following example illustrates the use of the global RegExp object.

  function matchDemo(){
     var s;
     var re = new RegExp("d(b+)(d)","ig");
     var str = "cdbBdbsbdbdz";
     var arr = re.exec(str);
     s = "$1 contains: " + RegExp.$1 + "\n";
     s += "$2 contains: " + RegExp.$2 + "\n";
     s += "$3 contains: " + RegExp.$3;
     return(s);

  }

  replace Method

  Returns a copy of a string with text replaced using a regular expression or search string.

  stringObj.replace(rgExp, replaceText)

  Arguments

  stringObj

  Required. The String object or string literal on which to perform the replacement. This string is not modified by the replace method.

  rgExp

  Required. An instance of a Regular Expression object containing the regular expression pattern and applicable flags. Can also be a String object or literal. If rgExp is not an instance of a Regular Expression object, it is converted to a string, and an exact search is made for the results; no attempt is made to convert the string into a regular expression.

  replaceText

  Required. A String object or string literal containing the text to replace for every successful match of rgExp in stringObj.  In JScript 5.5 or later, the replaceText argument can also be a function that returns the replacement text.

  Remarks

  The result of the replace method is a copy of stringObj after the specified replacements have been made.

  Any of the following match variables can be used to identify the most recent match and the string from which it came. The match variables can be used in text replacement where the replacement string has to be determined dynamically.

  Characters	Meaning
  $$	$ (JScript 5.5 or later)
  $&	Specifies that portion of stringObj that the entire pattern matched. (JScript 5.5 or later)
  $`	Specifies that portion of stringObj that precedes the match described by $&. (JScript 5.5 or later)
  $'	Specifies that portion of stringObj that follows the match described by $&. (JScript 5.5 or later)
  $n	The nth captured submatch, where n is a single decimal digit from 1 through 9. (JScript 5.5 or later)
  $nn	The nnth captured submatch, where nn is a two-digit decimal number from 01 through 99. (JScript 5.5 or later)

  
  

  If replaceText is a function, for each matched substring the function is called with the following m + 3 arguments where m is the number of left capturing parentheses in the rgExp. The first argument is the substring that matched. The next m arguments are all of the captures that resulted from the search. Argument m + 2 is the offset within stringObj where the match occurred, and argument m + 3 is stringObj. The result is the string value that results from replacing each matched substring with the corresponding return value of the function call.

  The replace method updates the properties of the global RegExp object.

  Example

  The following example illustrates the use of the replace method to replace the first instance of the word "The" with the word "A."

  function ReplaceDemo(){
     var r, re;                    //Declare variables.
     var ss = "The man hit the ball with the bat.\n";
     ss += "while the fielder caught the ball with the glove.";
     re = /The/g;             //Create regular expression pattern.
     r = ss.replace(re, "A");    //Replace "A" with "The".
     return(r);                   //Return string with replacement made.
  }

  In addition, the replace method can also replace subexpressions in the pattern. The following example swaps each pair of words in the string.

  function ReplaceDemo(){
     var r, re;                      //Declare variables.
     var ss = "The rain in Spain falls mainly in the plain.";
     re = /(\S+)(\s+)(\S+)/g;        //Create regular expression pattern.
     r = ss.replace(re, "$3$2$1");   //Swap each pair of words.
     return(r);                      //Return resulting string.
  }

  The following example, which works in JScript 5.5 and later, performs a Fahrenheit to Celsius conversion, illustrates using a function as replaceText. To see how this function works, pass in a string containing a number followed immediately by an "F" (e.g., "Water boils at 212”).

  function f2c(s) {
    var test = /(\d+(\.\d*)?)F\b/g;    //Initialize pattern.
    return(s.replace
      (test,
        function($0,$1,$2) { 
          return((($1-32) * 5/9) + "C");
        }
      )
    );
  }
  document.write(f2c("Water freezes at 32F and boils at 212F."));

  Requirements

  Version 1

  See Also

  exec Method | match Method | RegExp Object | search Method | String Object Methods | test Method

  Applies To: String Object

   

Etc

Society

Groupthink : Two Party System as Polyarchy : Corruption of Regulators : Bureaucracies : Understanding Micromanagers and Control Freaks : Toxic Managers :   Harvard Mafia : Diplomatic Communication : Surviving a Bad Performance Review : Insufficient Retirement Funds as Immanent Problem of Neoliberal Regime : PseudoScience : Who Rules America : Neoliberalism  : The Iron Law of Oligarchy : Libertarian Philosophy

Quotes

War and Peace : Skeptical Finance : John Kenneth Galbraith :Talleyrand : Oscar Wilde : Otto Von Bismarck : Keynes : George Carlin : Skeptics : Propaganda  : SE quotes : Language Design and Programming Quotes : Random IT-related quotes :  Somerset Maugham : Marcus Aurelius : Kurt Vonnegut : Eric Hoffer : Winston Churchill : Napoleon Bonaparte : Ambrose Bierce :  Bernard Shaw : Mark Twain Quotes

Bulletin:

Vol 25, No.12 (December, 2013) Rational Fools vs. Efficient Crooks The efficient markets hypothesis : Political Skeptic Bulletin, 2013 : Unemployment Bulletin, 2010 :  Vol 23, No.10 (October, 2011) An observation about corporate security departments : Slightly Skeptical Euromaydan Chronicles, June 2014 : Greenspan legacy bulletin, 2008 : Vol 25, No.10 (October, 2013) Cryptolocker Trojan (Win32/Crilock.A) : Vol 25, No.08 (August, 2013) Cloud providers as intelligence collection hubs : Financial Humor Bulletin, 2010 : Inequality Bulletin, 2009 : Financial Humor Bulletin, 2008 : Copyleft Problems Bulletin, 2004 : Financial Humor Bulletin, 2011 : Energy Bulletin, 2010 : Malware Protection Bulletin, 2010 : Vol 26, No.1 (January, 2013) Object-Oriented Cult : Political Skeptic Bulletin, 2011 : Vol 23, No.11 (November, 2011) Softpanorama classification of sysadmin horror stories : Vol 25, No.05 (May, 2013) Corporate bullshit as a communication method  : Vol 25, No.06 (June, 2013) A Note on the Relationship of Brooks Law and Conway Law

History:

Fifty glorious years (1950-2000): the triumph of the US computer engineering : Donald Knuth : TAoCP and its Influence of Computer Science : Richard Stallman : Linus Torvalds  : Larry Wall  : John K. Ousterhout : CTSS : Multix OS Unix History : Unix shell history : VI editor : History of pipes concept : Solaris : MS DOS :  Programming Languages History : PL/1 : Simula 67 : C : History of GCC development :  Scripting Languages : Perl history   : OS History : Mail : DNS : SSH : CPU Instruction Sets : SPARC systems 1987-2006 : Norton Commander : Norton Utilities : Norton Ghost : Frontpage history : Malware Defense History : GNU Screen : OSS early history

Classic books:

The Peter Principle : Parkinson Law : 1984 : The Mythical Man-Month :  How to Solve It by George Polya : The Art of Computer Programming : The Elements of Programming Style : The Unix Hater’s Handbook : The Jargon file : The True Believer : Programming Pearls : The Good Soldier Svejk : The Power Elite

Most popular humor pages:

Manifest of the Softpanorama IT Slacker Society : Ten Commandments of the IT Slackers Society : Computer Humor Collection : BSD Logo Story : The Cuckoo's Egg : IT Slang : C++ Humor : ARE YOU A BBS ADDICT? : The Perl Purity Test : Object oriented programmers of all nations : Financial Humor : Financial Humor Bulletin, 2008 : Financial Humor Bulletin, 2010 : The Most Comprehensive Collection of Editor-related Humor : Programming Language Humor : Goldman Sachs related humor : Greenspan humor : C Humor : Scripting Humor : Real Programmers Humor : Web Humor : GPL-related Humor : OFM Humor : Politically Incorrect Humor : IDS Humor : "Linux Sucks" Humor : Russian Musical Humor : Best Russian Programmer Humor : Microsoft plans to buy Catholic Church : Richard Stallman Related Humor : Admin Humor : Perl-related Humor : Linus Torvalds Related humor : PseudoScience Related Humor : Networking Humor : Shell Humor : Financial Humor Bulletin, 2011 : Financial Humor Bulletin, 2012 : Financial Humor Bulletin, 2013 : Java Humor : Software Engineering Humor : Sun Solaris Related Humor : Education Humor : IBM Humor : Assembler-related Humor : VIM Humor : Computer Viruses Humor : Bright tomorrow is rescheduled to a day after tomorrow : Classic Computer Humor

The Last but not Least Technology is dominated by two types of people: those who understand what they do not manage and those who manage what they do not understand ~Archibald Putt. Ph.D

The statements, views and opinions presented on this web page are those of the author (or referenced source) and are not endorsed by, nor do they necessarily reflect, the opinions of the Softpanorama society. We do not warrant the correctness of the information provided or its fitness for any purpose. The site uses AdSense so you need to be aware of Google privacy policy. You you do not want to be tracked by Google please disable Javascript for this site. This site is perfectly usable without Javascript.

Last modified: March, 12, 2019