JavaScript Regular Expressions 3

Question 1

What is a positive lookahead assertion in a regular expression?

Accepted Answer

A zero-width assertion that matches a position only if a specified pattern follows it

Answer

A group that captures and remembers a match for later

Answer

A backwards search that checks what came before the match

Answer

A flag that makes the regex look for multiple matches

Question 2

What does `(?<=...)` represent in a JavaScript regular expression?

Accepted Answer

A positive lookbehind assertion that checks what precedes the current position

Answer

A positive lookahead assertion

Answer

A non-capturing group with lazy matching

Answer

A named capture group

Question 3

What does the `s` (dotAll) flag do in a regular expression?

Accepted Answer

Allows `.` to match any character including newline (
)

Answer

Enables sticky matching from lastIndex

Answer

Makes the search case-insensitive

Answer

Enables matching of Unicode surrogates

Question 4

Given a regex with a named capture group `(?<year>\d{4})`, how do you access the captured value from a `match()` result?

Accepted Answer

result.groups.year

Answer

result[1]

Answer

result.named.year

Answer

result.captures.year

Question 5

What does `str.split(/,\s*/)` do?

Accepted Answer

Splits the string on each comma, discarding any spaces that immediately follow it

Answer

Splits only on commas with no surrounding whitespace

Answer

Removes all commas and spaces from the string

Answer

Splits on any whitespace character

Question 6

What does the `y` (sticky) flag do in a JavaScript regular expression?

Accepted Answer

Forces the match to start exactly at the regex's lastIndex position

Answer

Finds all matches globally throughout the string

Answer

Enables lazy (minimal) quantifier behavior

Answer

Enables multiline anchoring for ^ and $

Question 7

What does the quantifier `+?` mean in a regular expression?

Accepted Answer

A lazy (non-greedy) match of one or more occurrences, taking as few as possible

Answer

A greedy match of one or more occurrences, taking as many as possible

Answer

An optional match of exactly one occurrence

Answer

A possessive match that never backtracks