Regex

myRegex = /Hello/ <- literal string! myString = "Hello, world" myRegex.test(myString)

test () checks if string contains something matching regex and returns true or false

| <--- pipe (can be used for 'or')

Flags

Appended to regex to modify rules i = ignore case/case insensitive g = global (to search for pattern more than once)

Match

Extracts matches found in regex

myString.match(myRegex)

. (dot) - Wildcard!

. <--- period/dot = matches any one character

Character Sets

When you want to have several options for a character (like 'or') Example: /b[aiu]g/ would match bag, big, and bug Inside character set, you can use a hyphen to define a range

Negated Set

Match anything other than defined (use carat ^) Example: /[^aeiou]/gi matches anything not a vowel

+

To match a character or group of characters that appear one or more times in a row, use + Example: /a+/g would return 'a' for 'abc', 'aa', for 'aabc', 'a' for 'abab' and no match for 'bed'

_ (Asterisk)

To match zero or more occurrences, use _

Note to future self: Regex is character by character. If you see /an*/ig, that's really saying "look for a and it may or may not be followed by an 'n'" - works like a wildcard Asterisk can be used on character sets unlike wildcard dot (which only works iwth a single character)

Greedy match:

Longest possible match (default for regular expressions)

Lazy match:

Smallest possible part that satisfies regex pattern

Example: myString = "titantic" myRegex = /t[a-z]*i/ would return "titanti" myRegex = /t[a-z]*?i/ would return "ti"

$ (Anchor):

Anchor character searches for pattern at the end of a string.

Shorthand Character Classes:

\w is a shorthand equivalent to [A-Za-z0-9_] \W is shorthand equivalent to [^A-Za-z0-9_] \d is shorthand equivalent to [0-9] \D is shorthand equivalent to [^0-0] \s matches whitespace, carriage return, tab, form feed, newline - similar to [\r\t\f\n\v] \S is similar to [^\r\t\f\n\v]

Quantity Specifiers:

Range of repeat characters {num1, num2} Example: // match only if letter 'a' appears between 3 and 5 times in 'ah' myRegex = /a{3, 5}h/

To specify only lower limit, {num, } To specify the exact number of matches, {num}

?

To check for zero or more of a character

Lookaheads:

Checks to see if something is there, but doesn't match it.

Positive Lookahead (?= char):

Checks that an element is there

Negative Lookahead (?! char):

Checks that an element is not there

Capture Group:

Things in parentheses. Each capture group is numbered and can follow them with their number to indicate placement (so the number becomes like a variable reference). Example: /(waka) \1 \1 \1 sometimes maybe/gi matches: "waka waka waka waka sometimes maybe"