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

def matching_substrings(string, regex)
  string.size.times.each_with_object([]) do |start_index, maching_substrings|
    start_index.upto(string.size.pred) do |end_index|
      substring = string[start_index..end_index]
      maching_substrings.push(substring) if substring =~ /^#{regex}$/
    end
  end
end

matching_substrings('abcadc', /a.*c/) # => ["abc", "abcadc", "adc"]
matching_substrings('foobarfoo', /(\w+).*\1/) 
  # => ["foobarf",
  #     "foobarfo",
  #     "foobarfoo",
  #     "oo",
  #     "oobarfo",
  #     "oobarfoo",
  #     "obarfo",
  #     "obarfoo",
  #     "oo"]
matching_substrings('why is this downvoted?', /why.*/)
  # => ["why",
  #     "why ",
  #     "why i",
  #     "why is",
  #     "why is ",
  #     "why is t",
  #     "why is th",
  #     "why is thi",
  #     "why is this",
  #     "why is this ",
  #     "why is this d",
  #     "why is this do",
  #     "why is this dow",
  #     "why is this down",
  #     "why is this downv",
  #     "why is this downvo",
  #     "why is this downvot",
  #     "why is this downvote",
  #     "why is this downvoted",
  #     "why is this downvoted?"]