JavaScript Regular Expressions Quiz

To pass the quiz, you must correctly answer at least 18 of the 20 questions below. # --quizzes-- ## --quiz-- ### --question-- #### --text-- Which of the following is NOT a valid regular expression? #### --distractors-- ```js /hello, world!/i ``` --- ```js new RegExp("hello, world!") ``` --- ```js /(?:^|\s)hello[,]?\sworld[!]?(?:$|\s)/i ``` #### --answer-- ```js "hello, world!" ``` ### --question-- #### --text-- Which `RegExp` contains the same pattern as the regular expression `/f[o0]{2} b[a4@]r/i`? #### --distractors-- ```js new RegExp("/f[o0]{2} b[a4@]r/", "i") ``` --- ```js new RegExp("f[o0]{2} b[a4@]r", "g") ``` --- ```js new RegExp("f[o0]{2} b[a4@]r") ``` #### --answer-- ```js new RegExp("f[o0]{2} b[a4@]r", "i") ``` ### --question-- #### --text-- What is the return type for the regular expression method `test`? #### --distractors-- An array of strings that matched the regular expression. --- An object containing information about the (sub)string the regular expression matched. --- `null`, the method `test` only validates if the given regular expression is valid. #### --answer-- A boolean indicating whether the string matches the regular expression. ### --question-- #### --text-- What does the `match` method do when passed a regular expression without any flags? #### --distractors-- It searches for any strings that match the given regular expression, and returns ALL matches as an array. --- It searches for the first full match, and returns the starting index of that match. --- It searches for the first full match, and returns a boolean indicating whether or not a match was found. #### --answer-- It searches for the first full match, and returns an array containing that first match. ### --question-- #### --text-- Which is the best use case for `test`? #### --distractors-- For verifying a given regular expression. --- For getting detailed information about a string match, such as the length of the matched string. --- To extract all matches from a given string. #### --answer-- To check if a given string matches the regular expression. ### --question-- #### --text-- What is the purpose of using `replace`? #### --distractors-- To replace the current regular expression with a new regular expression. --- When given an index and a string, to replace the character at the specified index with the string provided. --- To remove all instances of a matched substring from a string. #### --answer-- To replace a matched string with a given replacement string. ### --question-- #### --text-- What is the difference between `match` and `matchAll`? #### --distractors-- `match` always returns a string, while `matchAll` always returns an array of matches. --- `match` returns a boolean indicating whether a match is found, while `matchAll` returns a number representing the amount of matches found. --- `match` returns a number indicating the starting index of the first match found, while `matchAll` returns an array of numbers containing indices where a match was found. #### --answer-- `match` returns an array of strings that match, while `matchAll` returns an iterator object of all matches found. ### --question-- #### --text-- Which of the following is the correct use of `replaceAll`? #### --distractors-- ```js foo.replaceAll(/foobar/, "fizzbuzz") ``` --- ```js foo.replaceAll(/foobar/i, "fizzbuzz") ``` --- ```js foo.replaceAll(/foobar/gi, /fizzbuzz/) ``` #### --answer-- ```js foo.replaceAll(/foobar/g, "fizzbuzz") ``` ### --question-- #### --text-- Which of the following character classes is equivalent to the regular expression `/[a-zA-Z0-9_]/`? #### --distractors-- `\d` --- `\s` --- `\n` #### --answer-- `\w` ### --question-- #### --text-- Which of the following character classes is most appropriate for extracting digits from a phone number? #### --distractors-- `\w` --- `\s` --- `\D` #### --answer-- `\d` ### --question-- #### --text-- What happens when a lookahead `(?=)` is used in a regular expression? #### --distractors-- The lookahead will assert to the left of the string, verifying that the sub-pattern IS present. --- A lookahead is an alternate regular expression pattern used when the main pattern fails to match. --- The lookahead will assert to the right of the string, verifying that the sub-pattern IS NOT present. #### --answer-- A lookahead asserts to the right of the string, verifying that the sub-pattern IS present. ### --question-- #### --text-- When making a regular expression, where should a lookbehind `(?<=)` be placed? #### --distractors-- The lookbehind can be placed anywhere in the regular expression. --- The lookbehind should be placed to the right of the main pattern of the regular expression. --- The lookbehind should include the main pattern of the regular expression. #### --answer-- The lookbehind should be placed to the left of the main pattern of the regular expression. ### --question-- #### --text-- Which quantifier matches the preceding element zero or one times? #### --distractors-- `+` --- `*` --- `a{0,}` #### --answer-- `?` ### --question-- #### --text-- Which of the following regular expressions only allows numbers between 0 and 999,999? #### --distractors-- `/^\d{6}$/` --- `/^\d{0, 999999}$/` --- `/^\d+$/` #### --answer-- `/^\d{1,6}$/` ### --question-- #### --text-- Which of the following statements is true about the custom character class (`[]`)? #### --distractors-- It's a set of characters to be removed from the match. --- It can define a set of characters to match without the need to escape any special characters. --- It represents a set of characters in Unicode form. #### --answer-- It can define a custom set of characters to match. ### --question-- #### --text-- Which of the following character classes correctly matches the uppercase alphabet? #### --distractors-- `\w` --- `[a-z]` --- `[AZ]` #### --answer-- `[A-Z]` ### --question-- #### --text-- What happens when a capturing group `(...)` is used in a regular expression? #### --distractors-- The capturing group is immediately evaluated, regardless of where it is located in the regular expression. --- The capturing group attempts to match using the given subpattern, and continues without memorizing the result. --- The capturing group is a prioritized subpattern, which will immediately return when a match is found for the subpattern. #### --answer-- The capturing group attempts to match using the given subpattern, and continues with the result in memory. ### --question-- #### --text-- What happens when a non-capturing group `(?:...)` is used in a regular expression? #### --distractors-- The non-capturing group attempts to match using the given subpattern, and continues with the result in memory. --- The non-capturing group immediately terminates when it finds a match for the given subpattern. --- The non-capturing group is considered an optional match, so only a successful match is added on the result. #### --answer-- The non-capturing group attempts to match using the given subpattern, and continues without keeping the result in memory. ### --question-- #### --text-- Given the following regular expression, which of these tests will return `true`? ```js const regex = /(cat)\s+\1/i; ``` #### --distractors-- ```js regex.test("cat dog cat"); ``` --- ```js regex.test("catcat"); ``` --- ```js regex.test("cat\s+cat"); ``` #### --answer-- ```js regex.test("cat cat"); ``` ### --question-- #### --text-- What does the wildcard character class (`.`) do in a regular expression? #### --distractors-- It matches only whitespace characters. --- It matches the start of a string. --- It matches a single digit. #### --answer-- It matches any single character except a newline.