How can you capture multiple groups in a JavaScript regexp when the repetition only keeps the last match?

Capturing Multiple Groups in JavaScript Regexp

When working with regular expressions in JavaScript, it is possible to capture multiple groups of matches within a string. However, there are limitations to the number of groups that can be captured and retrieved.

Consider the following JavaScript regexp:

"foo bar baz".match(/^(\s*\w+)+$/)

One might expect this regexp to return an array containing the entire string "foo bar baz" as well as each individual word:

["foo bar baz", "foo", " bar", " baz"]

However, the regexp actually returns only the last captured match:

["foo bar baz", " baz"]

This behavior occurs because, in most regexp flavors, only the last capture for a repeated capturing group is retained. In JavaScript, repeating a capturing group only allows for the capture of exactly the specified number of strings per match.

To overcome this limitation, there are several options:

• Splitting on delimiters: If possible, consider splitting the string on the appropriate delimiter instead of using a regexp with repeated capturing groups.
• Using a global exec loop: Match the repeated group in one match using the /pattern/g flag and then process the results using an exec loop. Note that this method is not entirely equivalent to a repeated capturing group.
• Multilevel matching: Capture the repeated group in one match and then use a second regexp to break that match apart.

Example:

To match the string in a text using multilevel matching:

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(";"));
}

This approach uses two levels of matching to extract individual words from the string.

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