REGEX

Question 1

How do you specify a unique character?

Answer 1

The simplest way is to add in the character itself to the REGEX.
i.e. a for ‘a’, D for ‘D’, and 3 for ‘3’.

Question 2

What if you wanted a or b or c, for a specific character index?

Answer 2

bracket notation [ ]
[abc] would match only “a” or “b” or “c”.

Question 3

What does \d match?

Answer 3

\d matches to ANY digit.

Question 4

What does \D match?

Answer 4

\D matches with any NON-digit.

Question 5

What is the REGEX notation for any character?

Answer 5

the period . is the marker for a wild card in regex

to notate a period it must be .

Question 6

What does \w match?

Answer 6

\w matches to any Alphanumeric character.

Question 7

What does \W match?

Answer 7

\W matches to any NON-alphanumeric character

Question 8

How do you express not “x”, nor “y”, nor “z” ?

Answer 8

[^xyz]
the index cannot have x nor y nor z.

Question 9

How would you match a range of characters?

Answer 9

With a dash -

for example to match capitalized names:
[A-Z][a-z] would match an uppercase character followed by a lowercase character.

Question 10

How do you specify repetitions?

Answer 10

with curly brackets and a comma.
{ , }

z{3, 5} would match zzz, zzzz, or zzzzz.

Question 11

How can you express zero or more repetition?

Answer 11

with the * character
aa* would match “”, “aa”, or “aaaa”.

Question 12

How can you express one or more repetitions?

Answer 12

with the + character
bb+ would match “bb”, “bbbbbb”, but not “”.

Question 13

How can you denote a character is option?

Answer 13

Follow the character with a ‘?’ to denote it is optional.

ab?c can match ac and abc.

Question 14

How can you match any whitespace?

Answer 14

with the \s expression.

Question 15

What does \S match to?

Answer 15

Any NON-whitespace

Question 16

How do you match a specific string?

Answer 16

within a ^ and $
^my string$ will only match “my string”.

Question 17

What are ^ … $

Answer 17

Outside of [] the ^ represents ‘starts with’

while $ represents ‘ends with’

for situations you have
^start\regex\end$
or
^startend$

Question 18

What do parenthesis do ( )

Answer 18

They create a ‘capture group’ to represent a sub-pattern within the REGEX

Question 19

How can you express ‘or’ withing a REGEX

Answer 19

With | (cat|dog)s
would be “cats” or “dogs”

Question 20

What does \b represent?

Answer 20

“Boundary Anchor”

It’s a zero-width assertion and does not consume any characters in the string.

Question 21

What are the four use cases for a Boundary Anchor

Answer 21

1) Word Boundary at the beginning or end ::
\btalk
matches “talk” at the beginning of the index.
talk\b
matches “talk” from the end of talk.

2) Whole word matching
\bMyWord\b

3) Excluding substrings
\bcat\b
matches “cat” but not concatenate.

4) Word Boundary in the Middle:

\bword1\b.*\bword2\b matches a pattern where “word1” and “word2” are whole words separated by any characters.