JavaScript Regular Expressions Basics Quiz
Answer 35 questions covering regex literal vs constructor syntax, metacharacters, character classes, quantifiers, anchors, grouping, escaping, and JS testing/matching methods.
35 Questions
~70 minutes
1
Question 1
How do you declare a regex literal in JavaScript?
A
/pattern/flags
B
regex(pattern)
C
<pattern>
D
new Pattern()
2
Question 2
When is RegExp constructor syntax preferred?
A
When the pattern is built dynamically from strings at runtime
B
When the pattern never changes
C
When regex features are disabled
D
When you need automatic escaping
3
Question 3
What logs?
javascript
const literal = /cat/i
const dynamic = new RegExp('cat', 'i')
console.log(literal.test('CAT'))
console.log(dynamic.test('Cat'))A
true true
B
false false
C
true false
D
false true
4
Question 4
What extra escaping is required when using the constructor?
A
Backslashes inside strings must be doubled (e.g., "\\d")
B
Dots must be tripled
C
Parentheses are disallowed
D
No escaping differences exist
5
Question 5
What does the dot (.) metacharacter match by default?
A
Any character except line terminators
B
Only digits
C
Only letters
D
Nothing; it is literal
6
Question 6
Which metacharacter matches a digit?
A
\d
B
\w
C
\s
D
\b
7
Question 7
What logs?
javascript
const regex = /a.c/
console.log(regex.test('abc'))
console.log(regex.test('ac'))A
true false
B
false true
C
true true
D
false false
8
Question 8
What does \s match?
A
Whitespace characters (space, tab, newline, etc.)
B
Only spaces
C
Only newlines
D
Any non-whitespace character
9
Question 9
What does [aeiou] represent?
A
Any single lowercase vowel
B
Exactly the string "aeiou"
C
Any vowel sequence
D
Vowels followed by consonants
10
Question 10
How do you negate a character class?
A
[^...] places caret first to match anything not listed
B
[...]^ at end
C
Use double brackets [[...]]
D
Negation is impossible
11
Question 11
What logs?
javascript
const regex = /gr[ae]y/
console.log(regex.test('gray'))
console.log(regex.test('grey'))
console.log(regex.test('groy'))A
true true false
B
true false true
C
false true false
D
false false true
12
Question 12
What does [^0-9] match?
A
Any character that is not a digit
B
Only digits
C
Digit sequences
D
Empty strings only
13
Question 13
What does the + quantifier mean?
A
One or more occurrences
B
Zero or one
C
Zero or more
D
Exactly one
14
Question 14
What logs?
javascript
const regex = /go+d/
console.log(regex.test('god'))
console.log(regex.test('good'))
console.log(regex.test('gd'))A
true true false
B
false true true
C
true false true
D
false false true
15
Question 15
What does {3,5} mean when used as a quantifier?
A
Between three and five occurrences inclusive
B
Exactly five occurrences
C
At most three occurrences
D
Unlimited occurrences
16
Question 16
Why should you beware of overly greedy quantifiers?
A
They may consume more text than intended, requiring extra logic or making matches fail
B
They disable regex flags
C
They slow down string creation
D
They remove anchors
17
Question 17
What does ^ represent in regex?
A
Start of input (or line in multiline mode)
B
Literal caret character
C
End of input
D
Negation of a class
18
Question 18
What logs?
javascript
const regex = /^cat/
console.log(regex.test('catfish'))
console.log(regex.test('scatter' ))A
true false
B
true true
C
false true
D
false false
19
Question 19
What does $ anchor?
A
End of input (or line in multiline mode)
B
Start of input
C
Word boundary
D
Decimal digits
20
Question 20
What logs?
javascript
const priceRegex = /\d+$/
console.log(priceRegex.test('Total: 20'))
console.log(priceRegex.test('20 USD'))A
true false
B
false true
C
true true
D
false false
21
Question 21
Why use parentheses in regex?
A
To group patterns for quantifiers and capture matched substrings
B
To comment the regex
C
To escape special characters
D
To match literal parentheses only
22
Question 22
What logs?
javascript
const regex = /(ha)+!/
console.log(regex.test('hahaha!'))
console.log(regex.test('ha!'))
console.log(regex.test('ha'))A
true true false
B
true false true
C
false true true
D
false false true
23
Question 23
How do non-capturing groups look?
A
(?:pattern)
B
(*pattern)
C
[pattern]
D
pattern?
24
Question 24
Why use non-capturing groups?
A
To group for alternation or quantifiers without populating capture groups
B
To speed up network requests
C
To auto-escape patterns
D
To enable lookbehind
25
Question 25
Which characters generally require escaping to match literally?
A
. ^ $ * + ? ( ) [ ] { } | \
B
Letters and digits
C
Whitespace only
D
No characters need escaping
26
Question 26
What logs?
javascript
const regex = /\./
console.log(regex.test('file.txt'))
console.log(regex.test('filetxt'))A
true false
B
false true
C
true true
D
false false
27
Question 27
Why must you double escape backslashes in string-based regex creation?
A
String literals treat backslash as escape, so to pass \ to RegExp you write \\
B
To reduce file size
C
To enable unicode
D
To disable multiline mode
28
Question 28
What does regex.test(string) return?
A
Boolean indicating whether the pattern matches
B
Array of matches
C
The original regex
D
Number of captures
29
Question 29
Why might RegExp.prototype.exec be preferred over test?
A
exec returns detailed match info including capture groups and indexes
B
exec is faster for booleans
C
exec disables globals
D
exec automatically converts patterns to strings
30
Question 30
What logs?
javascript
const regex = /(\d+)-(\w+)/
const result = regex.exec('Order 24-shipping')
console.log(result[0])
console.log(result[1])
console.log(result[2])A
'24-shipping', '24', 'shipping'
B
'Order', '24', 'shipping'
C
'24', 'shipping', undefined
D
null for all
31
Question 31
What does string.match(regex) return in ES2015 when regex has the g flag?
A
Array of all matches without capture groups
B
Single match array with groups
C
Boolean only
D
Iterator object
32
Question 32
What logs?
javascript
const matches = 'ababa'.match(/aba/g)
console.log(matches)
console.log(matches.length)A
['aba'] and 1
B
['aba', 'aba'] and 2
C
null and 0
D
['ab'] and 1
33
Question 33
How does String.prototype.matchAll help?
A
It returns an iterator with all matches including capture groups, even with global flag
B
It returns only the first match
C
It mutates the string
D
It disables regex flags
34
Question 34
What logs?
javascript
const regex = /\bcat\b/g
const str = 'cats catalog cat'
let match
const found = []
while ((match = regex.exec(str)) !== null) {
found.push(match[0])
}
console.log(found)A
['cat']
B
['cats', 'cat', 'catalog']
C
['cat', 'cat']
D
[]
35
Question 35
Why reset lastIndex when reusing global regex with exec?
A
Because exec with g flag maintains state; without reset it continues from previous position
B
Because lastIndex stores flags
C
Because resetting increases speed
D
Because regex requires caching