Repeated occurrences

So far, we saw how we can match fixed characters or numeric patterns. Most often, you want to handle certain repetitive natures of patterns also. For example, if I want to match 4 as, I can write /aaaa/, but what if I want to specify a pattern that can match any number of as?

Regular expressions provide you with a wide variety of repetition quantifiers. Repetition quantifiers let us specify how many times a particular pattern can occur. We can specify fixed values (characters should appear n times) and variable values (characters can appear at least n times till they appear m times). The following table lists the various repetition quantifiers:

  • ?: Either 0 or 1 occurrence (marks the occurrence as optional)
  • *: 0 or more occurrences ...

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