Extended and properly-multi-line Regular Expressions for JavaScript at George MacKerron: code blog

Extended and properly-multi-line Regular Expressions for JavaScript

Perl, Ruby, and some other languages support a readable ‘extended’ regular expression syntax, in which literal whitespace is ignored and comments (starting with #) are available. They also support a multi-line mode where the . character matches anything, including a newline.

JavaScript does neither of these: it doesn’t recognise the extended syntax, and its version of multi-line only allows the ^ and $ characters to match the beginnings and ends of lines within a string (it will never allow the . to match a newline).

So I wrote the following function to convert extended and fully-multi-line RegExp source strings to the basic syntax that JavaScript understands.

function convertRegExpSource(source, ext, multi) {  // string, boolean, boolean
  if (! ext && ! multi) return source;
  var convertedSource = '', len = source.length;
  var inCharClass = false, inComment = false, justBackslashed = false;
  for (var i = 0; i < len; i ++) {
    var c = source.charAt(i);
    if (justBackslashed) {
      if (! inComment) convertedSource += c;
      justBackslashed = false;
      continue;
    }
    if (c == '\\') {
      if (! inComment) convertedSource += c;
      justBackslashed = true;
      continue;
    }
    if (inCharClass) {
      convertedSource += c;
      if (c == ']') inCharClass = false;
      continue;
    }
    if (inComment) {
      if (c == "\n" || c == "\r") inComment = false;
      continue;
    }
    if (c == '[') {
      convertedSource += c;
      inCharClass = true;
      continue;
    }
    if (ext && c == '#') {
      inComment = true;
      continue;
    }
    if (multi && c == '.') {
      convertedSource += '[\\s\\S]';
      continue;
    }
    if (! ext || ! c.match(/\s/)) convertedSource += c;
  }
  return convertedSource;
}

Use it

The starting example below is the Daring Fireball monster URL regex.

Extended RegExp source (editable)

\b ( # Capture 1: entire matched URL (?: [a-z][\w-]+: # URL protocol and colon (?: /{1,3} # 1-3 slashes | # or [a-z0-9%] # Single letter or digit or '%' # (Trying not to match e.g. "URI::Escape") ) | # or www\d{0,3}[.] # "www.", "www1.", "www2." … "www999." | # or [a-z0-9.\-]+[.][a-z]{2,4}/ # looks like domain name followed by a slash ) (?: # One or more: [^\s()<>]+ # Run of non-space, non-()<> | # or $([^\s()<>]+|(\([^\s()<>]+$))*\) # balanced parens, up to 2 levels )+ (?: # End with: $([^\s()<>]+|(\([^\s()<>]+$))*\) # balanced parens, up to 2 levels | # or [^\s`!()\[\]{};:'".,<>?«»“”‘’] # not a space or one of these punct chars ) )

Basic RegExp source output

Let me know if you find any bugs, or if you know a nicer way to do this (I know nothing about parsing, so there surely is one).

I think I may suggest extended RegExp support as a possible CoffeeScript enhancement.

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Written by George

August 8th, 2010 at 7:44 pm

Posted in JavaScript

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KaylaGTurnball1590

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KaylaGTurnball1590

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KaylaGTurnball1590

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KaylaGTurnball1590

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KaylaGTurnball1590

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KaylaGTurnball1590

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KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b
KaylaGTurnball1590

Good to know. I also can share my experience in filling forms. You’ll forget about paperwork when you try PDFfiller. NY DTF ET-30 can be filled out in 5-10 mins here http://goo.gl/pVaG1b

George MacKerron: code blog