How to capture an arbitrary number of groups in JavaScript Regexp?
JavascriptRegexRepeatCapturing GroupJavascript Problem Overview
I would expect this line of JavaScript:
"foo bar baz".match(/^(\s*\w+)+$/)
to return something like:
["foo bar baz", "foo", " bar", " baz"]
but instead it returns only the last captured match:
["foo bar baz", " baz"]
Is there a way to get all the captured matches?
Javascript Solutions
Solution 1 - Javascript
When you repeat a capturing group, in most flavors, only the last capture is kept; any previous capture is overwritten. In some flavor, e.g. .NET, you can get all intermediate captures, but this is not the case with Javascript.
That is, in Javascript, if you have a pattern with N capturing groups, you can only capture exactly N strings per match, even if some of those groups were repeated.
So generally speaking, depending on what you need to do:
- If it's an option, split on delimiters instead
- Instead of matching
/(pattern)+/
, maybe match/pattern/g
, perhaps in anexec
loop- Do note that these two aren't exactly equivalent, but it may be an option
- Do multilevel matching:
- Capture the repeated group in one match
- Then run another regex to break that match apart
References
Example
Here's an example of matching <some;words;here>
in a text, using an exec
loop, and then splitting on ;
to get individual words (see also on ideone.com):
var text = "a;b;<c;d;e;f>;g;h;i;<no no no>;j;k;<xx;yy;zz>";
var r = /<(\w+(;\w+)*)>/g;
var match;
while ((match = r.exec(text)) != null) {
print(match[1].split(";"));
}
// c,d,e,f
// xx,yy,zz
The pattern used is:
_2__
/ \
<(\w+(;\w+)*)>
\__________/
1
This matches <word>
, <word;another>
, <word;another;please>
, etc. Group 2 is repeated to capture any number of words, but it can only keep the last capture. The entire list of words is captured by group 1; this string is then split
on the semicolon delimiter.
Related questions
Solution 2 - Javascript
How's about this? "foo bar baz".match(/(\w+)+/g)
Solution 3 - Javascript
Unless you have a more complicated requirement for how you're splitting your strings, you can split them, and then return the initial string with them:
var data = "foo bar baz";
var pieces = data.split(' ');
pieces.unshift(data);
Solution 4 - Javascript
try using 'g':
"foo bar baz".match(/\w+/g)
Solution 5 - Javascript
You can use LAZY evaluation. So, instead of using * (GREEDY), try using ? (LAZY)
REGEX: (\s*\w+)?
RESULT:
Match 1: foo
Match 2: bar
Match 3: baz