Uber Front end Developer Interview Questions and Answers

1 Hr coding round, Leetcode medium problems like Minimum Grid sum & Basic calculator

Q1. What is denbouncer and throttle
Ans. 
Debouncer and throttle are techniques used to limit the frequency of function calls.
• Debouncing delays the execution of a function until a certain amount of time has passed without the function being called again.

• Throttling limits the frequency of function calls to a certain rate, executing the function at fixed intervals.

• Debouncing is useful for events that may be triggered multiple times in quick succession, such as r...read more
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Q2. What is curry function
Ans. 
Currying is a technique of transforming a function that takes multiple arguments into a sequence of functions that each take a single argument.
• Currying allows partial application of a function

• It helps in creating reusable functions

• Curried functions are easier to compose and chain

• Example: const add = (a) => (b) => a + b; add(2)(3) returns 5
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Q3. Implement curry function
Ans. 
Curry function is a higher-order function that allows partial application of arguments.
• Currying transforms a function that takes multiple arguments into a series of functions that take one argument each.

• It returns a new function until all the arguments are received and then executes the original function.

• Example: const add = (a, b) => a + b; const curriedAdd = curry(add); curriedAdd(2)(3) returns 5.
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Q4. What is promise.all()
Ans. 
promise.all() is a method that takes an array of promises and returns a new promise that resolves when all promises in the array have resolved.
• It is used to handle multiple asynchronous operations simultaneously.

• If any of the promises in the array rejects, the returned promise will be rejected with the reason of the first rejected promise.

• The resolved values of the promises are returned as an array in the same order as
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Q5. What is memoization?
Ans. 
Memoization is a technique of caching the results of a function to improve performance.
• Memoization is used to avoid redundant calculations by storing the results of a function and returning the cached result when the same inputs occur again.

• It is commonly used in recursive functions and functions with expensive computations.

• Memoization can be implemented manually or by using libraries like Lodash or Memoizee.

• Example: M...read more
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Q6. What is closure in javascript
Ans. 
Closure is a function that has access to its parent scope even after the parent function has returned.
• Closure allows for private variables and functions in JavaScript.

• It is created when a function returns another function.

• The inner function has access to the outer function's variables and parameters.

• Example: function outer() { let x = 10; return function inner() { console.log(x); } }

• The inner function can access and mo...read more
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Q7. What is the problem with colosures
Ans. 
Closures can cause memory leaks if not handled properly.
• Closures can hold references to variables outside of their scope, preventing them from being garbage collected.

• If closures are used excessively or not released properly, they can cause memory leaks.

• To avoid memory leaks, make sure to release closures when they are no longer needed.
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Q8. Some output questions on SetTimeout to check closure knowledge
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Q9. React lifecycle events
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Q10. Major difference between class based components and class based components
Ans. 
There is no difference between class based components and class based components.
• There seems to be a typo in the question.

• Assuming the question is about functional components vs class components, the major difference is that class components use a class to define the component while functional components are defined as functions.

• Class components have access to lifecycle methods while functional components do not.

• Functi...read more
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Q11. Shallow copy vs deep copy
Ans. 
Shallow copy only copies the reference to an object while deep copy creates a new object with a new memory address.
• Shallow copy is faster and uses less memory than deep copy.

• In shallow copy, changes made to the original object will reflect in the copied object as well.

• Deep copy creates a completely new object with its own memory space.

• In JavaScript, arrays and objects are assigned by reference, so a shallow copy will o...read more
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Q12. How to do deep copy ?
Ans. 
Deep copy creates a new object with the same values as the original object.
• Use Object.assign() method to create a deep copy of an object.

• For nested objects, use recursion to copy all levels.

• For arrays, use slice() method to create a new array with the same values.

• Avoid using spread operator for deep copy as it only creates a shallow copy.
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Q13. What is hoisting? Some questions on it
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Coding a frontend UI from provided image. And creating a fucntional star rating system

Q1. Designing a Component API in React using Typescript.
Ans. 
Designing a Component API in React using Typescript involves defining props, state, and methods for the component.
• Define the props interface to specify the expected input data for the component

• Use typescript types to ensure type safety and prevent runtime errors

• Define the state interface to manage the internal state of the component

• Implement methods to handle user interactions and component logic

• Document the component
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Q2. Create a function that can clear all the timer ids at once.
Ans. 
Function to clear all timer ids at once
• Create an array to store all timer ids

• Iterate through the array and clear each timer id using clearTimeout() function
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30mins aptitude test

90 mins coding test for 3 questions

Q1. Why are you choosing this role
Ans. 
I am choosing this role because of my passion for creating user-friendly and visually appealing websites.
• Passion for front end development

• Enjoy creating user-friendly interfaces

• Excited about the creative aspect of web design
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Q2. Why should we write you
Ans. 
I am a dedicated and skilled front end developer with a passion for creating user-friendly interfaces.
• I have a strong understanding of HTML, CSS, and JavaScript

• I have experience with responsive design and cross-browser compatibility

• I am proficient in using front end frameworks like React and Angular
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Q1. Given a matrix zeros and ones find minimum distance for each one to a zero.
Ans. 
Given a matrix of zeros and ones, find the minimum distance for each one to a zero.
• Use breadth-first search (BFS) to find the minimum distance from each one to a zero.

• Start by initializing a queue with all the zeros in the matrix.

• While the queue is not empty, dequeue a zero and enqueue its neighboring ones.

• Keep track of the distance from each one to the nearest zero.

• Repeat until all ones have been visited.

• Return the ma
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