Regular Expressions

• .test() - takes regular expression (regex), applies it to a string (which is placed inside the parenthesis) & returns true or false depending if the pattern is found or not

Example:

• use alternation or OR operator: | (pipe)

  • matches pattern before and after it

Example:

/yes | no/

• use "i" flag

Example:

/ignore case/i

• will match this pattern regardless if any is capitalized or not

• .match() - extract the actual match

  • apply the method on a string and pass in the regex pattern inside the parenthesis

Example:

• use "g" flag

Example:

• the wildcard "." will match any one character

Example:

• search for a literal pattern with character classes

• character classes allow you to define a group of characters

  • place them inside []

Example:

• want to match beg, bug, big but not bog

Regex: /b[eiu]g/

• include letters and numbers: /[A-Za-z0-9]/

• equivalent to \w: /\w/

• exclude letters and numbers: /[^A-Za-z0-9]/

• equivalent to \W: /\W/

Example:

• useful for when you want to search ahead for multiple patterns

  • positive look ahead: (?=...)

  • negative look ahead: (?!...)

• ?: possible existence of previous character if exact number

character class: /[0-9]/ or shorthand \d: /\d/

character class: /[^0-9]/ or shorthand \D: /\D/

1. can only use alpha-numeric characters

2. can not begin with numbers and must only be at the end ( can ne zero or more at the end only)

3. letters can by upper or lower case

4. use name must be at least two characters long and if only two characters, must be alpha characters only (no numbers)

Examples:

s1: /^[a-z][a-z]+\d*\S|^[a-z]\d\d+\S/i

s2: /^[a-z]([0-9]{2,}|[a-z+\d*)\S]/i

• {2,}: ends with two or more numbers

• {3, 5}: between 3 and 5 times

• {}: quantity specifiers

• +: 1 or more characters

• *: 0 or more characters

• \S: non-white spaces

• character class: [^/r/t/f/n/v]

• s = space

• r = carriage return

• t = tab

• f = form feed

• n = new line

• v = vertical tab