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01.07 Using Quantifiers

Let’s examing below expression one by one:

(\d{3,4}[.-]?)+

• (: open a capturing group
• \: start character shorthand (escape the following character)
• d: match all Arabic digits, like [0-9]
• {3,4}: match 3 or 4 of the preceding character
  • {: open a quantifier
  • 3: match 3 of the preceding character
  • ,: separate the min and max values
  • 4: match 4 of the preceding character
  • }: close the quantifier
• [.-]?: match 0 or 1 of the preceding character
  • [: open a character class
  • .: match any character
  • -: leteral character to match a hyphen
  • ]: close the character class
  • ?: match 0 or 1 of the preceding character
• ): close the capturing group
• +: match 1 or more of the preceding character

Improved expression:

(\d{3}[.-]?){2}\d{4}

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Date: 2025/04/28

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