Regex basics
By convention regular expressions are enclosed in ‘//’ — /regex/.
A simple string as a regex matches a string containing this regex.
/example/
'here is an example'
Anchors: ^$
/^example/
'example one:' - this will match
'here is an example' — this won't match
/example$/
'example one:' — this won't match
'here is an example' — this will
Quantifiers: *+?{}
* — 0, 1 or more
/pears*/
'pear', 'pears', 'pearss', ...
+ — 1 or more
/pears+/
'pears', 'pearss', ...
'pear' won't match
? — 0 or 1
/pears?/
'pear', 'pears'
{} — number of occurances
/pears{2}/
'pearss'
/pears{2,}/
'pearss', 'pearsss', ...
/pears{2,4}/
'pearss', 'pearsss', 'pearssss'
Classes
\d— single digit\w- single ‘word’ character (letter, digit, underscore)\s- single whitespace.- single anything\D- single non-digit\W- single non-‘word’ character-
\S- single non-whitespace [A-Z]— all capital latin letters[a-z]— all small latin letters[A-Za-z]— combined[0-9]— all digits
[^] expresses negation (e.g. [^0-9] — non-digits)