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Introduction to Regular Expressions
Review

Do you feel those regular expression superpowers coursing through your body? Do you just want to scream ah+ really loud? Awesome! You are now ready to take these skills and use them out in the wild. Before beginning your adventures, let’s review what we’ve learned.

  • Regular expressions are special sequences of characters that describe a pattern of text that is to be matched
  • We can use literals to match the exact characters that we desire
  • Alternation, using the pipe symbol |, allows us to match the text preceding or following the |
  • Character sets, denoted by a pair of brackets [], let us match one character from a series of characters
  • Wildcards, represented by the period or dot ., will match any single character (letter, number, symbol or whitespace)
  • Ranges allow us to specify a range of characters in which we can make a match
  • Shorthand character classes like \w, \d and \s represent the ranges representing word characters, digit characters, and whitespace characters, respectively
  • Groupings, denoted with parentheses (), group parts of a regular expression together, and allows us to limit alternation to part of a regex
  • Fixed quantifiers, represented with curly braces {}, let us indicate the exact quantity or a range of quantity of a character we wish to match
  • Optional quantifiers, indicated by the question mark ?, allow us to indicate a character in a regex is optional, or can appear either 0 times or 1 time
  • The Kleene star, denoted with the asterisk *, is a quantifier that matches the preceding character 0 or more times
  • The Kleene plus, denoted by the plus +, matches the preceding character 1 or more times
  • The anchor symbols hat ^ and dollar sign $ are used to match text at the start and end of a string, respectively

Instructions

The interactive applet in the browser allows you to enter a regular expression and see if it matches a string of text. If a character is matched, you’ll see it highlighted in green. If there’s a checkmark next to the string, you’ve completely matched the whole piece of text!

Enter a regular expression that matches each of the telephone numbers listed below “Match these strings”. This is a tricky one, so have some fun. Good luck!

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