RegEx

Question 1

what the test() method does

Answer 1

takes the regex, applies it to a string (which is placed inside the parentheses), and returns true or false if your pattern finds something or not.

let testStr = “freeCodeCamp”;
let testRegex = /Code/;
testRegex.test(testStr);
// Returns true

Question 2

search for multiple patterns using the

Answer 2

alternation or OR operator: |

if you wanted to match “yes” or “no”, the regex you want is /yes|no/.

Question 3

match both cases using

Answer 3

a flag

You can use it by appending it to the regex. An example of using this flag is /ignorecase/i. This regex can match the strings “ignorecase”, “igNoreCase”, and “IgnoreCase”

Question 4

extract actual matches with ___

Answer 4

match() method

Question 5

To search or extract a pattern more than once…

Answer 5

use the g flag

Question 6

what the wildcard character . does

Answer 6

will match any one character

if you wanted to match “hug”, “huh”, “hut”, and “hum”, you can use the regex /hu./ to match all four words

Question 7

what are character classes

Answer 7

Character classes allow you to define a group of characters you wish to match by placing them inside square [ ] brackets.

Question 8

match “bag”, “big”, and “bug” but not “bog”

Answer 8

/b[aiu]g/

Question 9

define a range of characters to match

Answer 9

[a-e] finds characters a to e

Question 10

/[0-5]/ matches

Answer 10

any number between 0 and 5 including 0 and 5

Question 11

matches all letters and numbers in word

Answer 11

/[a-z0-9]/ig

Question 12

create a negated character set with

Answer 12

you place a caret character (^) after the opening bracket and before the characters you do not want to match.

/[^aeiou]/gi matches all characters that are not a vowel

Question 13

how to match a character (or group of characters) that appears one or more times in a row

Answer 13

use the + character

Question 14

find matches when the letter s occurs one or more times in “Mississippi”

Answer 14

/s+/g

Question 15

option that matches characters that occur zero or more times

Answer 15

asterisk or star: *

Question 16

greedy vs lazy match

Answer 16

a greedy match finds the longest possible part of a string

a lazy match finds the smallest possible part of the string

Question 17

Regular expressions are by default {greedy or lazy?)

Answer 17

greedy

Question 18

you can use the ____ character to change it to lazy matching

Answer 18

?

Question 19

“titanic” matched against the adjusted regex of /t[a-z]*?i/ returns

Answer 19

[“ti”]

Question 20

“titanic” matched against the adjusted regex of /t[a-z]*i/ returns

Answer 20

[“titani”]

Question 21

Parsing HTML with regular expressions should be ____

Answer 21

avoided

Question 22

Outside of a character set, the caret (^) is used to search for patterns at

Answer 22

the beginning of strings.

let firstString = “Ricky is first and can be found.”;
let firstRegex = /^Ricky/;
firstRegex.test(firstString);
// Returns true

Question 23

You can search the end of strings using _____ at the end of the regex

Answer 23

the dollar sign character $

Question 24

The closest character class in JavaScript to match the alphabet is ___

Answer 24

\w

Question 25

\w shortcut is equal to

Answer 25

[A-Za-z0-9_]

Note, this character class also includes the underscore character (_).

Question 26

You can search for the opposite of the \w with

Answer 26

\W

Note, the opposite pattern uses a capital letter. This shortcut is the same as [^A-Za-z0-9_]

Question 27

the shortcut for digits is

Answer 27

\d

this is equal to [0-9]

Question 28

the opposite of digits is

Answer 28

\D

this is equal to [^0-9]

Question 29

match whitespace

Answer 29

\s

also matches carriage return, tab, form feed, and new line characters

Question 30

opposite of whitespace

Answer 30

\S

Question 31

specify the lower and upper number of patterns with quantity specifiers

Answer 31

{ and }

to match only the letter a appearing between 3 and 5 times in the string “ah”, your regex would be /a{3,5}h/

let ohStr = "Ohhh no";
let ohRegex = /Oh{3,6} no/; 
// would match Oh, Ohh, Ohhh, Ohhhh, Ohhhhh, Ohhhhhh
let result = ohRegex.test(ohStr);

Question 32

To only specify the lower number of patterns,

Answer 32

keep the first number followed by a comma.

{3,}

to match only the string “hah” with the letter a appearing at least 3 times, your regex would be /ha{3,}h/.

Question 33

specify a certain number of patterns

Answer 33

just have that one number between the curly brackets.

to match only the word “hah” with the letter a 3 times, your regex would be /ha{3}h/

Question 34

specify the possible existence of an element with a

Answer 34

?

This checks for zero or one of the preceding element. You can think of this symbol as saying the previous element is optional.

let american = "color";
let british = "colour";
let rainbowRegex= /colou?r/;
rainbowRegex.test(american); // Returns true
rainbowRegex.test(british); // Returns true

Question 35

Lookaheads are patterns that tell JavaScript

Answer 35

to look-ahead in your string to check for patterns further along. This can be useful when you want to search for multiple patterns over the same string.

Question 36

There are two kinds of lookaheads:

Answer 36

positive lookahead and negative lookahead.

Question 37

A positive lookahead

Answer 37

will look to make sure the element in the search pattern is there, but won’t actually match it.

Question 38

A positive lookahead is used as

Answer 38

(?=…) where the … is the required part that is not matched.

Question 39

a negative lookahead will look to make sure the element in the search pattern is

Answer 39

not there

Question 40

A negative lookahead is used as

Answer 40

(?!…) where the … is the pattern that you do not want to be there.

Question 41

The rest of the pattern is _____ if the negative lookahead part is not present.

Answer 41

returned

Question 42

A more practical use of lookaheads is

Answer 42

to check two or more patterns in one string

Question 43

check for groups of characters

Answer 43

using ()

Question 44

search for repeat substrings

Answer 44

capture groups

Question 45

To specify where that repeat string will appear

Answer 45

backslash () and then a number. This number starts at 1 and increases with each additional capture group you use. An example would be \1 to match the first group.

Question 46

capture just 3 repeating patterns of digits separated by space

Answer 46

let repeatNum = "42 42 42";
let reRegex = /^(\d+)(\s)\1\2\1$/; // Change this line
let result = reRegex.test(repeatNum);

Question 47

ou can search and replace text in a string using

Answer 47

.replace()

Question 48

The inputs for .replace() is first _____. The second parameter is ____

Answer 48

(1) the regex pattern you want to search for

(2) the string to replace the match

Question 49

You can also access capture groups in the replacement string with _____ like _____

Answer 49

dollar signs $

like this

"Code Camp".replace(/(\w+)\s(\w+)/, '$2 $1');
// Returns "Camp Code"

Question 50

How to replicate String.prototype.trim() in regex (code)

Answer 50

let hello = “ Hello, World! “;
let wsRegex = /(\s+)(\w+,\s\w+!)(\s+)/; // create 3 groups, 2 for whitespace at both ends, and one in the middle for words - and keep it
let result = hello.replace(wsRegex,”$2”);