Dev

run: http-server -p 2380
view at: http://localhost:2380/demo/

Regex Syllabus

Introduction to Regex

AKA: learning the concept & reasons

• What is it for?
  • Finding desired patterns within strings of text
  • Treats everything as sequence of characters
• Basic syntax
  • Delimiter / ... /
  • flags / ... /igm
    • g: iterative search
    • i: ignore case (case insensitive)
    • m: multiline support

Regex Lessons

AKA: learning the commands

• Literal identifier
  • /literal/matches "literal"
  • Matching everything .
    • /.*/
  • Searching with Or |
    • /everything|something/
  • Anchors
    • Match start of string: /^pattern/
    • Match end of string: /pattern$/
• Carrot functions & importance of placement
  • /^literal/ will match "literal lesson"
  • /^literal/ will not match "Something literal"
  • /^[literal]/ will match anything except "literal"
  • /literal$/ will match "Something literal"
• Escaping characters
  • Preceed character wth\ e.g.: \.
• • Matching everything
  • /./ matches all characters including whitespaces
  • escape . to match lteral period
• Quantifiers: repeating with +
  • + matches one or more of preceeding pattern
  • l{1,3} matches one to three repeated instances of letter l
  • ? is used to make a pattern optional
    • /pie?/ matches pi
• Shortcut classes vs long the way
  • \d vs [0-9]
  • \w vs [a-zA-Z]
  • \D vs ^[a-zA-Z]
  • Capture Groups
    • Use parentheses around multiple tokesn to group them together, similar to math
    • /Greg(ory)?/i matches greg and gregory
    • Probably not included in the game
      • Backreferences \1Used to repeat the previous pattern
      • Named groups
        • (?<mygroup>[abc])=\k<mygroup> same as ([abc])=\1

Pratice Tasks & Challenges

AKA: Applying the knowledge

• Match every version of hello except the last
  • q: hello helllllllo helllo helo
  • a: /hel{2,6}o/
• Match only the digits
  • q: abc123xyz
  • a: /\d/ or /[1-3]/
• Match everything except last string
  • q: bird. mouse. house
  • a: /.*\./
• Match every other word (requires array of strings with three or more words)
• Remove repeating characters
• Match valid .com web addresses
  • ^(http|https):\/\/+[\www\d]+\.[\w]+(\/[\w\d]+)?
• Remove comma from number
• Match all zeros
• Match these email addresses (stacked enemies?)
• Match these phone numbers (stacked?)
• English & British spelling
• Matching the hard way (with easy characters locked)

Real World Use Cases

AKA: What regex can do for you

• Optional Characters (match alternate spellings)
  • neighbo?ur
  • apologize || apologise
  • Jan(uary)?
  • {3}(.)?
• Match email addresses
  • /[a-z0-9._%+-]+@[a-z0-9.-]+\.[a-z]{2,4}/
  • /^.+@.+$/
• Format phone numbers
  • /((\<1[\-\. ])?(\(|\<)\d\d\d[\)\.\-/ ] ?)?\<\d\d\d[\.\- ]\d\d\d\d\>/
• SSN
  • /\<\d\d\d[\- ]\d\d[\- ]\d\d\d\d\>/
• Remove comma from number
  • TBD
• Find HTML tag
  • <([A-Z][A-Z0-9]*)\b[^>]*>(.*?)</\1>
  • <title>(.*)</title>
• Trimming whitespace
  • ^[ \t]+|[ \t]+$
  • [ \t\r\n]
• Matching valid date
  • ^(19|20)\d\d([- /.])(0[1-9]|1[012])\2(0[1-9]|[12][0-9]|3[01])$
• Credit card numbers
  • /\<((\d\d\d\d)[\- ]){3}\d\d\d\d\>/
• Find or format currency [$ and 2 decimals]
  • ^[+-]?[0-9]{1,3}(?:,?[0-9]{3})*\.[0-9]{2}$