Regular expressions in JS (select tags from string)

Question

I have this string:

some description +first tag, +second tag (tags separated by commas)
+third tag +fourth tag (tags separated by space)
+tag from new line (it's just one tag)
+tag1+tag2+tag3 (tags can follow each other)

How can I select all tag names from this string?

1) Tag can contain several words, 2) tag always starts with + sign, 3) tag ends with either next tag, or newline, or comma

I've tried to split the string by lines, then by ','. So I have array of substrings. Then I need to extracts tags from each substring. It's a little bit easy than from initial string, but I still don't know how to do it :) — Ildar
– Ildar, Commented Mar 4, 2013 at 2:18
so what result are you after? Something like {first: "tag",second: "tag (tags sepearated by commas}",third: "tag",fourth: "tag (tags separated by space)",tag:"from new line (it's just one tag)", tag1tag2tag3 : "(tags can follow each other)"} — OJay
– OJay, Commented Mar 4, 2013 at 2:38

loganfsmyth · Accepted Answer · 2013-03-04 02:59:43Z

2

I'd give this a shot:

var str = "some description +first tag, +second tag\n" +
   "+third tag +fourth tag\n" +
   "+tag from new line\n" +
   "+tag1+tag2+tag3";
var tags = str.match(/\+[^+,\n\s].+?(?=\s*[\+,\n]|$)/g);

this results in tags with this:

[ '+first tag',
  '+second tag',
  '+third tag',
  '+fourth tag',
  '+tag from new line',
  '+tag1',
  '+tag2',
  '+tag3' ]

To elaborate:

\+          // Starts with a '+'.
[^+,\n\s]   // Doesn't end immedatedly (empty tag).
.+?         // Non-greedily match everything.
(?=         // Forward lookahead (not returned in match).
  \s*       // Eat any trailing whitespace.
  [\+,\n]|$ // Find tag-ending characters, or the end of the string.
)

edited Mar 4, 2013 at 2:59

answered Mar 4, 2013 at 2:38

loganfsmyth

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5 Comments

Ildar Over a year ago

it doesn't grab the last tag "tag3"

Ildar Over a year ago

ok, I can append an additional \n at the end of the string :)

mVChr Over a year ago

You need to add $ to your lookahead (i.e. (?=\s*([\+,\n]|$))), but +1

Ildar Over a year ago

It's almost as awesome as this: topito.com/wp-content/uploads/2013/01/code-03.gif

loganfsmyth Over a year ago

@mVChr Good call, updated. @Iidar, adding the $ is a better way that adding an extra \n.

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