Interviewing at Facebook — On-Site JavaScript Technical Interview Questions

Adi S
Adi S
Jan 29 · 2 min read

The Microsoft and Google Assessments have been popular and readers are asking for more examples!


Here are some questions from an on-site technical interview at Facebook in 2019.


You are a product manager and currently leading a team to develop a new product. Unfortunately, the latest version of your product fails the quality check. Since each version is developed based on the previous version, all the versions after a bad version are also bad.

Suppose you have n versions [1, 2, ..., n] and you want to find out the first bad one, which causes all the following ones to be bad.

You are given an API bool isBadVersion(version) which will return whether version is bad. Implement a function to find the first bad version. You should minimize the number of calls to the API.


Given n = 5, and version = 4 is the first bad isBadVersion(3) -> false
call isBadVersion(5) -> true
call isBadVersion(4) -> true
Then 4 is the first bad version.


Design a data structure that supports the following two operations:

void addWord(word)
bool search(word)

search(word) can search a literal word or a regular expression string containing only letters a-z or .. A . means it can represent any one letter.


search("pad") -> false
search("bad") -> true
search(".ad") -> true
search("b..") -> true

You may assume that all words are consist of lowercase letters a-z.

Given a 2d grid map of '1's (land) and '0's (water), count the number of islands. An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the grid are all surrounded by water.

Example 1:

Output: 1

Example 2:

Output: 3


Remove the minimum number of invalid parentheses in order to make the input string valid. Return all possible results.

Note: The input string may contain letters other than the parentheses ( and ).

Example 1:

Input: "()())()"
Output: ["()()()", "(())()"]

Example 2:

Input: "(a)())()"
Output: ["(a)()()", "(a())()"]

Example 3:

Input: ")("
Output: [""]

Like last week, I will post the questions and will wait for answers in the comments before posting my solution. Think about time/space complexity when submitting answers. Please submit answers in JavaScript.

Good luck! Note: These were quite difficult and seems like even more difficult in person.

JavaScript in Plain English

Learn the web's most important programming language.

Adi S

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Adi S

JavaScript in Plain English

Learn the web's most important programming language.

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