How to get possibly overlapping matches in a string

Question

I\'m looking for a way, either in Ruby or Javascript, that will give me all matches, possibly overlapping, within a string against a regexp.

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Let\'s say I have

Answer 1

Here's an approach that is similar to @ndn's and @Mark's that works with any string and regex. I've implemented this as a method of String because that's where I'd like to see it. Wouldn't it be a great compliment to String#[] and String#scan?

class String
  def all_matches(regex)
    return [] if empty?
    r = /^#{regex}$/
    1.upto(size).with_object([]) { |i,a|
      a.concat(each_char.each_cons(i).map(&:join).select { |s| s =~ r }) }
  end
end

'abcadc'.all_matches /a.*c/
  # => ["abc", "abcadc", "adc"]
'aaabaaa'.all_matches(/a.*a/)
  #=> ["aa", "aa", "aa", "aa", "aaa", "aba", "aaa", "aaba", "abaa", "aaaba",
  #    "aabaa", "abaaa", "aaabaa", "aabaaa", "aaabaaa"]