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Microsoft Frontend Engineer Coding Questions

45 practice questions for Microsoft Frontend Engineer interviews

Microsoft frontend engineer interviews emphasise JavaScript, DOM manipulation, CSS, accessibility, browser APIs, and UI component architecture.

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coding Medium Verified Question #1

1. Design Rate Limiter


Category: Sliding window coding problem
# Design Rate Limiter Design a rate limiter system that controls the number of requests allowed within a specified time window. The rate limiter is...
Input: String
Output: Computed result
coding Medium Verified Question #2

2. Object Oriented Design - Idempotent Receipt Sending


Category: Trie-based coding problem
Input: String
Output: Computed result
coding Medium Verified Question #3

3. Object Oriented Design - Notification Service


Category: Trie-based coding problem
# Problem Statement Design a notification service that supports sending notifications through multiple channels (SMS, Email) and is architected to...
Input: Number(s)
Output: Computed result
coding Medium Verified Question #4

4. Shortest Substring with N Unique Characters


Category: String coding problem
# Shortest Substring with N Unique Characters *This is a variation of the leetcode problem* Given a string s and an integer n, find the length of...
Input: String
Output: Computed result
coding Hard Verified Question #5

5. Rate Limiter


Category: Sliding window coding problem
Design a rate limiter that tracks API requests per client and enforces limits using a sliding time window. Your system must support: - hit(key,...
Input: Given input
Output:** Computed result
coding Hard Verified Question #6

6. Non-Adjacent Team Selection


Category: Tree coding problem
# Question You are given n people labeled from 0 to n - 1. Some pairs of people know each other directly. These relationships are given as a...
Input: List
Output: Computed result
coding Medium Verified Question #7

7. Bounded Repeat Substring


Category: String coding problem
A sensor data stream is represented as a string of characters. A contiguous segment of the stream is considered valid if it contains no three...
Input: String
Output: Computed result
coding Medium Verified Question #8

8. OA [CodeSignal] Prime Jumps


Category: Algorithm coding problem
# OA [CodeSignal] Prime Jumps A game is played with the following rules: - A player starts at cell 0 with a score of 0. - There is a row of n cells...
Input: Number(s)
Output: Computed result
coding Hard Verified Question #9

9. Combine N-ary Trees


Category: Tree coding problem
You are given the roots of two N-ary organization charts, each representing a hierarchical department structure. Every node has an integer...
Input: List
Output: Computed result
coding Medium Verified Question #10

10. Digit Replacement Maximizer


Category: String coding problem
A numeric optimization system performs exactly k substitution operations on a number string s. In each operation, choose any digit in s that is...
Input: String
Output: Computed result
coding Medium Verified Question #11

11. Best Window For Target Count


Category: Trie-based coding problem
A log analysis tool searches for the most frequent occurrence of a specific error code within a fixed-size window of log entries. Given an integer...
Input: Array
Output: Integer
coding Medium Verified Question #12

12. Evens Before Odds


Category: Array coding problem
You are given an integer array nums. Rearrange nums so that all even numbers appear before all odd numbers. The relative order of even or odd...
Input: Array
Output: Integer
coding Hard debouncing #1

1. [OA] Debouncing — Implement a debounce function for user input in Office 365

Users in Microsoft Office 365 often face lag in interface responsiveness due to multiple rapid inputs. Implement a debounce function to enhance user experience by limiting the rate of function executions.
Define a method debounce(func, wait) that returns a debounced version of the given function which ensures the function is invoked after a delay only if it hasn't been called within the wait period.
Example 1:
Input: const debouncedFunc = debounce(() => console.log('Action'), 1000); debouncedFunc(); (followed by another call within 1 sec)
Output: No output, because the function has not fired due to debouncing
Constraints:
- wait is a non-negative integer.
- The debounced function can be called at most 10^6 times.
coding Medium closure #2

2. [OA] Closure — Implement a counter that tracks user actions in Edge

Microsoft Edge needs to track user actions such as clicks to improve user experience through analytics. Using closures, implement a simple action counter.
The Counter class should support the following methods:
- increment() -> void: Increases the count by 1.
- getCount() -> number: Returns the current count.
Example 1:
Input: const counter = new Counter(); counter.increment(); counter.increment(); counter.getCount();
Output: 2
Explanation: The counter was incremented twice, so it returns 2.
Constraints:
- The count will never be negative.
- There will be at most 10^6 calls to the methods.

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