Demystifying the Wizardry of Regular Expressions - LV DotNet Meetup - 01/2016

So many developers see the words "Regular Expressions" and think of a frightening string of crazy symbols. While this is true, they are also a valuable way of manipulating text and knowing the basics can lead to many practical uses that will often save many lines of code. Learning to use regular expression basics will allow many more ways to manipulate text and strings by testing, extracting, and changing the string. We will take a look at some of the ways to do this specifically using the Javascript RegExp Engine.

Transcript

1. Regular Expression Wizardry
   Josiah Mory @kickinbahk
   

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2. Let’s set the stage…
   

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3. /^[\w+\-.]+@[a-z\d\-]+(\.[a-z\d\-]+)*\.[a-z]+$/i
   

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5. /^[\w+\-.]+@[a-z\d\-]+(\.[a-z\d\-]+)*\.[a-z]+$/i
   

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7. Maybe someone was having
   a bad day
   

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8. What is a Regular
   Expression?
   

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9. Regular Expression
   =
   a pattern describing a
   specific string of text
   

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10. /regex-pattern-here/
    

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11. /[a-z]/
    

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12. Regular Expression "Engine"
    =
    a piece of software which
    processes regular expressions
    and tries to match the pattern
    to the given string
    

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13. The syntax and
    behavior of a particular
    engine
    =
    regular expression flavor
    

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14. 3 Things You Do with
    Regular Expressions
    

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15. Search
    a string to see if it matches your
    pattern
    

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16. Extract
    a string (or part of a string) that matches
    your pattern
    

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17. Replace
    a string by replacing parts that match
    with other text
    

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18. “Find-and-Replace on Steroids”
    - Dan Nguyen
    

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19. Literal Characters
    

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20. Most Characters:
    • a - z
    • A - Z
    • 0 - 9
    

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21. Special Characters
    

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22. \, ^, $, ., |, ?, *, +, (, ), [, [,
    12 special or (meta) characters
    

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23. * If you want to use any of these
    characters as a literal in a regex, you
    need to escape them with a backslash
    

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27. gandalf_quote1 = "You shall not pass! -Gandalf"
    ~> You shall not pass! -Gandalf The Grey
    the_grey = “ The Grey”
    console.log(gandalf_quote + the_grey);
    

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28. gandalf_quote2 = "Yes, yes my dear sir and I do know your name Mr.
    Bilbo Baggins. And you do know my name, though you don't
    remember that I belong to it. I am Gandalf ” + the_grey + “ and
    Gandalf ” + the_grey + “ means me."
    gandalf_quote2 = "Yes, yes my dear sir and I do know your name Mr.
    Bilbo Baggins. And you do know my name, though you don't
    remember that I belong to it. I am Gandalf, and Gandalf, means me."
    

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30. Lookaheads
    ✤ Negative - ?!
    ✤ Positive - ?=
    

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31. Asserts that what
    immediately follows the
    current position in the string
    is not foo
    Negative Lookahead
    (?!foo)
    

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32. Asserts that what
    immediately follows the
    current position in the string
    is foo
    Positive Lookahead
    (?=foo)
    

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33. Capture Groups
    () allow us to group a RegEx
    together
    

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34. Groups are numbered 1-99
    

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35. You can call a Group using $ and
    the number
    E.g. $1
    

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36. To not capture a group in parens
    ?:
    

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37. /.*\.com\/(?:(?:groups\/videos\/)|
    (?:ondemand|channels)(?:(?:\/less\/)|(?:\/
    \w*\/))|(?:video\/))?([0-9]+).*/
    

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38. /.*\.com\/
    (?:(?:groups\/videos\/)|(?:ondemand|
    channels)(?:(?:\/less\/)|(?:\/\w*\/))|(?:video
    \/))?([0-9]+).*/
    

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39. /.*\.com\/
    (?:(?:groups\/videos\/)
    |(?:ondemand|channels)(?:(?:\/less\/)|(?:\/
    \w*\/))|(?:video\/))?([0-9]+).*/
    

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40. /.*\.com\/
    (?:(?:groups\/videos\/)
    |(?:ondemand|channels)(?:(?:\/less\/)
    |(?:\/\w*\/))|(?:video\/))?([0-9]+).*/
    

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41. /.*\.com\/
    (?:(?:groups\/videos\/)
    |(?:ondemand|channels)(?:(?:\/less\/)
    |(?:\/\w*\/))
    |(?:video\/))?([0-9]+).*/
    

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42. /.*\.com\/
    (?:(?:groups\/videos\/)
    |(?:ondemand|channels)(?:(?:\/less\/)
    |(?:\/\w*\/))
    |(?:video\/))?([0-9]+).*/
    

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43. /.*\.com\/
    (?:(?:groups\/videos\/)
    |(?:ondemand|channels)(?:(?:\/less\/)
    |(?:\/\w*\/))
    |(?:video\/))?([0-9]+).*/
    

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44. /.*\.com\/
    (?:(?:groups\/videos\/)
    |(?:ondemand|channels)(?:(?:\/less\/)
    |(?:\/\w*\/))
    |(?:video\/))?([0-9]+).*/
    

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45. /.*\.com\/
    (?:(?:groups\/videos\/)
    |(?:ondemand|channels)(?:(?:\/less\/)
    |(?:\/\w*\/))
    |(?:video\/))?([0-9]+).*/
    

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46. /.*vimeo.com\/
    (?:(?:groups\/videos\/)
    |(?:ondemand|channels)(?:(?:\/less\/)
    |(?:\/\w*\/))
    ?(?:video\/))?(?:[0-9]+)?.*/
    

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47. /.*\.com\/
    (?:(?:groups\/videos\/)
    |(?:ondemand|channels)(?:(?:\/less\/)
    |(?:\/\w*\/))
    |(?:video\/))?([0-9]+).*/
    /.*vimeo.com\/
    (?:(?:groups\/videos\/)
    |(?:ondemand|channels)(?:(?:\/less\/)
    |(?:\/\w*\/))
    ?(?:video\/))?(?:[0-9]+)?.*/
    

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48. https://vimeo.com/ondemand/less/101677664
    https://vimeo.com/channels/everythinganimated
    https://vimeo.com/152376671
    https://www.youtube.com/watch?v=RvYmwo7Tlu0
    

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49. Javascript The Good Parts (Chap 7) - Douglas Crockford
    RegExer - RegEx Tester and Editor for Javascript
    http://regexr.com/
    Eloquent Javascript (Chap 9) - Marijn Haverbeke
    http://eloquentjavascript.net/09_regexp.html
    MDN (Mozilla Developer Network) on Regular Expressions
    https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/
    Regular_Expressions
    Josiah’s Github
    https://github.com/kickinbahk/
    Regular_Expressions_LV_DotNet_Meetup_01-2016
    

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