Regex Basics

Question 1

Backslash \

Answer 1

escapes the character

Question 2

The Pipe |

Answer 2

Or

Question 3

The Question mark ?

Answer 3

The last item is optional, betyder att nåt får komma 0 eller 1 gång

Question 4

Parentheses

Answer 4

Used when you want to match several outcomes

Question 5

Square brackets []

Answer 5

Match only one out of a set or a range of characters

Question 6

Braces {}

Answer 6

When you want to repeat the last item, or set a range how of the minimum and maximum repeats

Question 7

The Dot .

Answer 7

Match any character except linebreaks

Question 8

The + Sign

Answer 8

Matches one or more of the former items, betyder att nåt måste komma minst en gång

Question 9

The * sign

Answer 9

Stars will match zero or more of the previous items, betyder ingenting eller hur mycket som helst

Question 10

The .* Sign

Answer 10

get everything.

Question 11

The Caret ^

Answer 11

match only strings that start exactly with

Question 12

The Caret in brackets [^0-9]

Answer 12

match only characters that are not right after the caret.

Question 13

The dollar sign $

Answer 13

don’t match if the target string has any characters beyond where I have placed the dollar sign

Question 14

\w

Answer 14

word

Question 15

\d

Answer 15

digit

Question 16

\s

Answer 16

whitespace

Question 17

\W

Answer 17

not word

Question 18

\D

Answer 18

not digit

Question 19

\S

Answer 19

not whitespace

Question 20

g flag

Answer 20

Global flag With this flag the search looks for all matches, without it – only the first match is returned.

Question 21

i flag

Answer 21

Ignore case sensitivity, With this flag the search is case-insensitive: no difference between A and a (see the example below).

Question 22

m flag

Answer 22

multiline flag, Multiline mode (covered in the chapter Multiline mode of anchors ^ $, flag “m”).

Question 23

\b

Answer 23

word boundary

Question 24

\t

Answer 24

escape tab

Question 25

\n

Answer 25

escape linefeed

Question 26

\r

Answer 26

escape carriage return

Question 27

\1

Answer 27

backreference to group #1

Question 28

(?:abc)

Answer 28

non-capturing group

Question 29

(?=abc)

Answer 29

positive lookahead

Question 30

(?!abc)

Answer 30

negative lookahead

Question 31

a*

Answer 31

0 or more

Question 32

a+

Answer 32

1 or more

Question 33

a?

Answer 33

0 or 1

Question 34

a{5} a{2,}

Answer 34

exactly 5, two or more

Question 35

a{1,3}

Answer 35

between one and 3

Question 36

a+? a{2,}?

Answer 36

match as few as possible

Question 37

u flag

Answer 37

Enables full unicode support. The flag enables correct processing of surrogate pairs. More about that in the chapter Unicode: flag “u” and class \p{…}.

Question 38

Metacharacter

Answer 38

Metacharacters are the building blocks of regular expressions. Characters in RegEx are understood to be either a metacharacter with a special meaning or a regular character with a literal meaning.