Introduction of basic building blocks in regular expressions example repetition token, anchor token, character token etc. Includes some challenges. (solutions included as well)

1. Regular Expressions
Part 1: Basic Building Blocks

2. What is a regular
expression?

3. Simple, an expression used regularly!

5. /ah/
Yes that is a regular expression!

6. You don’t believe me, try http://rubular.com/r/31xqIzPmPe
/aah/

7. Wonder how you’ll match
/aaaaaaaa...h/

8. Repetition Token
Token Property Regex Example Test String
{m, n} Match exact
occurrences of a
character/token
a{1,3}h ah, aah, aaah, aaaah,
h, ha, aha
? Matches 0 or 1
occurrence of a
token
a?h ah, aah, aaah, aaaah,
h, ha, aha
+ Matches 1 or more
occurrence of a
token
a+h ah, aah, aaah, aaaah,
h, ha, aha
* Matches 0 or more
occurrence of a
token
a*h ah, aah, aaah, aaaah,
h, ha, aha

9. Repetition Token
Token Property Regex Example Test String
{m, n} Match exact
occurrences of a
character/token
a{1,3}h ah, aah, aaah, aaaah,
h, ha, haaha
? Matches 0 or 1
occurrence of a
token
a?h ah, aah, aaah, aaaah,
h, ha, haaha
+ Matches 1 or more
occurrence of a
token
a+h ah, aah, aaah, aaaah,
h, ha, haaha
* Matches 0 or more
occurrence of a
token
a*h ah, aah, aaah, aaaah,
h, ha, haaha
Challenge 1:
Highlight the
first match for
string in
orange

10. Anchor Token
Token Property Regex Example Test String
^ Matches the
position at the start
of Line
^ah ah, aah, ha, aha,
ha<newline>ah
$ Matches the
position at the end
of Line
ah$ ah, aah, ha, aha,
ah<newline>ha
A Matches the
position at the start
of String
Aah ah, aah, ha, aha,
ha<newline>ah
Z Matches the
position at the end
of String
ahZ ah, aah, ha, aha,
ah<newline>ha

11. Character Token
Token Property Regex Example Test String
[a-zA-Z0-9] Matches one out of
several characters
gr[ea]y grey, gray, greay
[^a-zA-Z0-9] Matches any
character which is
not one of those in
the character set.
q[^u] qatar, Iraq,
[a-zA-Z0-9]+ Matches repeating
characters
[0-9]+ 333, 222, 123
[1st - [2nd]] Matches any one
character in first list
but not in the
second list.
[0-9-[02468]]+ 1357, 124, 111

12. Shortcut Character Token
Token Property Regex Example Test String
d Matches any digit d{1,9} 1, 123456789,
1234235259
s Matches any
whitespace
character
s+$ t, blank line with
spaces.
w Matches any word
character i.e.
letters, numbers, _
w{1,5} foo_1, $foo_1
D, S, W Matches opposite of
the above character
classes.
D+ Foobar, hello
world123!

13. Challenge 2:
Match 10 digit
mobile number
entered by user on
your signup form.

14. Ultimate Character - The .
The dot matches one of any character except the line break.

15. Challenge 2
^d{10,10}$
^$: Are anchor tags to
anchor to start and end of
input, prevents matching
abc0000000000
{10, 10}: matches
specifically 10 numbers
Solutions
Challenge 1
/a{1,3}h/ haaha
/a?h/ haaha
/a+h/ haaha
/a*h/ haaha

16. Let’s not get greedy.
We’ll dive deeper later!

17. Questions?