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
2. Let’s set the stage…
3. /^[\w+\-.]+@[a-z\d\-]+(\.[a-z\d\-]+)*\.[a-z]+$/i
5. /^[\w+\-.]+@[a-z\d\-]+(\.[a-z\d\-]+)*\.[a-z]+$/i
7. Maybe someone was having a bad day
8. What is a Regular Expression?
9. Regular Expression = a pattern describing a specific string of text
10. /regex-pattern-here/
11. /[a-z]/
12. Regular Expression "Engine" = a piece of software which processes regular expressions and tries to match the pattern to the given string
13. The syntax and behavior of a particular engine = regular expression flavor
14. 3 Things You Do with Regular Expressions
15. Search a string to see if it matches your pattern
16. Extract a string (or part of a string) that matches your pattern
17. Replace a string by replacing parts that match with other text
18. “Find-and-Replace on Steroids” - Dan Nguyen
19. Literal Characters
20. Most Characters: • a - z • A - Z • 0 - 9
21. Special Characters
22. \, ^, $, ., |, ?, *, +, (, ), [, [, 12 special or (meta) characters
23. * If you want to use any of these characters as a literal in a regex, you need to escape them with a backslash
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);
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."
30. Lookaheads ✤ Negative - ?! ✤ Positive - ?=
31. Asserts that what immediately follows the current position in the string is not foo Negative Lookahead (?!foo)
32. Asserts that what immediately follows the current position in the string is foo Positive Lookahead (?=foo)
33. Capture Groups () allow us to group a RegEx together
34. Groups are numbered 1-99
35. You can call a Group using $ and the number E.g. $1
36. To not capture a group in parens ?:
37. /.*\.com\/(?:(?:groups\/videos\/)| (?:ondemand|channels)(?:(?:\/less\/)|(?:\/ \w*\/))|(?:video\/))?([0-9]+).*/
38. /.*\.com\/ (?:(?:groups\/videos\/)|(?:ondemand| channels)(?:(?:\/less\/)|(?:\/\w*\/))|(?:video \/))?([0-9]+).*/
39. /.*\.com\/ (?:(?:groups\/videos\/) |(?:ondemand|channels)(?:(?:\/less\/)|(?:\/ \w*\/))|(?:video\/))?([0-9]+).*/
40. /.*\.com\/ (?:(?:groups\/videos\/) |(?:ondemand|channels)(?:(?:\/less\/) |(?:\/\w*\/))|(?:video\/))?([0-9]+).*/
41. /.*\.com\/ (?:(?:groups\/videos\/) |(?:ondemand|channels)(?:(?:\/less\/) |(?:\/\w*\/)) |(?:video\/))?([0-9]+).*/
42. /.*\.com\/ (?:(?:groups\/videos\/) |(?:ondemand|channels)(?:(?:\/less\/) |(?:\/\w*\/)) |(?:video\/))?([0-9]+).*/
43. /.*\.com\/ (?:(?:groups\/videos\/) |(?:ondemand|channels)(?:(?:\/less\/) |(?:\/\w*\/)) |(?:video\/))?([0-9]+).*/
44. /.*\.com\/ (?:(?:groups\/videos\/) |(?:ondemand|channels)(?:(?:\/less\/) |(?:\/\w*\/)) |(?:video\/))?([0-9]+).*/
45. /.*\.com\/ (?:(?:groups\/videos\/) |(?:ondemand|channels)(?:(?:\/less\/) |(?:\/\w*\/)) |(?:video\/))?([0-9]+).*/
46. /.*vimeo.com\/ (?:(?:groups\/videos\/) |(?:ondemand|channels)(?:(?:\/less\/) |(?:\/\w*\/)) ?(?:video\/))?(?:[0-9]+)?.*/
47. /.*\.com\/ (?:(?:groups\/videos\/) |(?:ondemand|channels)(?:(?:\/less\/) |(?:\/\w*\/)) |(?:video\/))?([0-9]+).*/ /.*vimeo.com\/ (?:(?:groups\/videos\/) |(?:ondemand|channels)(?:(?:\/less\/) |(?:\/\w*\/)) ?(?:video\/))?(?:[0-9]+)?.*/
48. https://vimeo.com/ondemand/less/101677664 https://vimeo.com/channels/everythinganimated https://vimeo.com/152376671 https://www.youtube.com/watch?v=RvYmwo7Tlu0
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