JavaScript Regular Expressions

Question 1

Which method tests whether a regular expression matches a string and returns a boolean?

Accepted Answer

regex.test(str)

Answer

str.match(regex)

Answer

regex.exec(str)

Answer

str.search(regex)

Question 2

What does the `g` flag do when added to a regular expression like `/abc/g`?

Accepted Answer

Finds all matches instead of stopping after the first

Answer

Makes matching case-insensitive

Answer

Enables multiline mode

Answer

Makes `.` match newline characters

Question 3

Which character class shorthand matches any single digit (0–9)?

Accepted Answer

\d

Answer

\w

Answer

\s

Answer

Question 4

What does `^` mean when placed at the very start of a regex pattern (outside a character class)?

Accepted Answer

Asserts the match must start at the beginning of the string

Answer

Negates the entire pattern

Answer

Matches zero or more of the preceding token

Answer

Matches any character except a newline

Question 5

What does `String.prototype.replace(regex, newValue)` return when passed a regular expression?

Accepted Answer

A new string with the matched portion replaced

Answer

The number of replacements made

Answer

The original string (strings are immutable)

Answer

An array of replacement results

Question 6

What does the shorthand `\w` match in a regular expression?

Accepted Answer

Any alphanumeric character or underscore ([A-Za-z0-9_])

Answer

Any whitespace character

Answer

Any word at a word boundary

Answer

Any non-word character

Question 7

What does the `i` flag do in a JavaScript regular expression?

Accepted Answer

Makes the pattern match regardless of letter case

Answer

Enables global matching across the string

Answer

Enables multiline mode for `^` and `$`

Answer

Enables the sticky matching mode