Regex

Question 1

see if the word ‘bobcat’ has an ‘o’ in it

Answer 1

> /o/.test(‘bobcat’)
= true

Question 2

see if the word ‘bobcat’ has an ‘l’ in it

Answer 2

> /l/.test(‘bobcat’)
= false

Question 3

What’s the difference between .test and .exec?

Answer 3

the exec() method will return the specified match if present or null if not present in the given string whereas the test() method returns a Boolean result

Question 4

How would you capture the char after ‘the’ in ‘The big dog jumps’?

Answer 4

let string ‘The big dog jumps’;
let regex= /[tT]he(.)/g;
let result = regex.exec(string)

//will capture the char after ‘The’

Question 5

How do we create a capture group?

Answer 5

using ().

Question 6

How do we name a capture group? and then use that capture group

Answer 6

using ?<name> at the beginning of our group definition</name>

let namedRegex = /[Tt]he(?<charAfterThe>.)/g
let namedResult = namedRegex.exec(string)
let charAfter = namedResult.groups.charAfterThe</charAfterThe>

Question 7

how would you match all 4 or 5 letter words

Answer 7

/\w{4,5}/

Question 8

match any word after the word ‘the’

Answer 8

/(?<=[tT]he )\w+/g

Question 9

match any word before the word ‘the’

Answer 9

/\w*(?= [tT]he)/g

Question 10

+

Answer 10

matches one or more in a row
ie /e+/g will find all ‘e’ or multiple ‘e’ substrings

Question 11

?

Answer 11

• optional
• ie /e+a?/g will find all ‘e’ or ‘ee’ or ‘ea’ substrings
• also changes * when chained ?. makes the behavior non-greedy. repetition will first try to match asfew*reps as possible

Question 12

*

Answer 12

• match 0 or more
• ie /re*/g will find all ‘r’ or ‘re’ or ‘ree’

Question 13

.

Answer 13

matches anything except a newline

Question 14

\

Answer 14

escape char
if you need to seach say for a period you can say /./g

Question 15

\w

Answer 15

matches any word char, so any letter

Question 16

\W

Answer 16

will match anything thats NOT a word char

Question 17

\s

Answer 17

will match any white space

Question 18

\S

Answer 18

matches anything that is not white space

Question 19

\d

Answer 19

matches any number digit

Question 19

\b

Answer 19

enforces a word break

function hasThanks(str) {
return /\b(thanks|thank you)\b/i.test(str);
}

hasThanks(“Thanks! You helped me a lot.”); // true
hasThanks(“Just want to say thank you for all your work.”); // true
hasThanks(“Thanksgiving is around the corner.”); // false

Question 20

{}

Answer 20

• specifies the number of chars
• /\w{4}/ will get any 4 letter words
• /\w{4,6}/ will get any words between 4 and 6 letters

Question 21

[]

Answer 21

• matches any chars inside the brackets
• /[ft]at/g will find all 3 letter words starting with f or t and ending in at.
• words with ranges [a-z] or [0-9A-Z]

Question 22

()

Answer 22

• allows you to create groupings
• anything after the grouping will affect the whole grouping ie /(t|e|r){2,3}/ will capture any 2 to 3 character long string of t, r, and e
• these groups are also called capture groups and allow you to ‘capture’ each group to modify it later
• (t|T) allows you to match lower case t or upper caseT
• (t|T)he matches any occurrence of ‘the’ or ‘The’
• (re){2,3} will find any instances of ‘rere’ or ‘rerere’

Answer 23

• match only to the beginning of the line.
• ^T will find capital T at the beginning of the line
• WHEN USE INSIDE A CHAR GROUP CAN ALSO BE USED TO REPRESENT NOT
  
  • ie [^s] means match any char that isnt S

Question 24

$

Answer 24

matches to the end of the statement