An overview of Regular Expressions, with examples

Reg Exp.md

Flags

Flag	Description	Truthy Example	Falsey Example
^	Matches the beginning of input	/^b/.test("bananas")	/^ananas/.test("bananas")
\	In effect reverses the 'specialness' of a letter	/\bb/.test("bananas")	/b\b/.test("bananas")
$	Matches the end of input	/anas$/.test("bananas")	/banan$/.test("bananas")
*	Matches the preceeding expression 0 or more times	/bananas*/.test("banana") or /bananas*/.test("bananasssssssss")	/(bananas)*/.test("monkey")
+	Matches the preceeding expression 1 or more times	/bananas+/.test("bananasss")	/bananas+/.test("banana")
?	Matches the preceeding character 0 or 1 time	/ba?na?na?/.exec("banana") // => ["banana"] or /ba?na?na?/.exec("bnn") // => ["bnn"]	/ba?na?na?/.exec("bana") // => null
.	Matches any character except newline	/monkey./.test("monkeys") // => true	/monkey./.test("monkey") // => false
(x)	Capturing parenthesis: remembers the match for use in future, in a replace for example
{n}	Matches exactly n occurrences of the preceeding expression	/monke{3}/.exec("monkeeeees") // => ["monkeee"]	/moon {1}keys/.test("moonkeys")
{n,m}	Matches at least n and at most m occurrences of the preceeding expression	/che{1,2}se/.test("cheese")	/che{3,5}se/.test("cheese")
[abc]	Character set. Matches any one of the characters
[^abc]	Negates the above
\b	Matches word boundaries
\B	Matches non-word boundaries
\d	Matches a digit character
\D	Matches a non-digit character
\r	Matches a carriage return
\s	Matches any white space character
\S	Matches any non-white space character
\t	Matches a tab
\w	Matches any alphanumeric character, or underscore
\W	Matches any non-alphanumeric character, or underscore