Blackrock Backend Developer Interview Questions and Answers

A hackerrank test was shared which had 2 ques to be solved in 60 min in Node.JS. The first one was a simple DS question related to arrays. The second ques was to write routes and controllers for a Node.JS Express app. The routes were GET /projects, GET /project/:id and GET /projects/active

Q1. What is the difference between package and package-lock.json?
Ans. 
package.json lists dependencies and package-lock.json ensures consistent installs.
• package.json lists all the dependencies required for the project

• package-lock.json ensures that the same versions of dependencies are installed across all environments

• package.json is manually edited while package-lock.json is generated automatically

• package-lock.json is used for reproducible builds
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Q2. Write a function that can keep a count of certain functions in our application.
Ans. 
Function to count certain functions in the application
• Create a dictionary to store the count of each function

• Increment the count of the function each time it is called

• Include a reset function to reset the count of all functions

• Example: def count_functions(): function_count = {}

• Example: def function1(): function_count['function1'] += 1

• Example: def reset_count(): function_count.clear()
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Q3. How can we make sure that package versions are taken from package-lock.json and not package.json
Ans. 
To ensure package versions are taken from package-lock.json, use npm ci instead of npm install.
• npm ci installs packages based on package-lock.json

• npm install may update package versions in package.json

• Always commit package-lock.json to version control
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Q4. Create an object and write a function inside it.
Ans. 
Creating an object with a function inside it.
• Create an object using object literal notation

• Define a function inside the object using function expression or declaration

• Access the function using object.method() syntax
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Q5. Given an array that has stock prices from morning till afternoon. Return the best buy and sell price to gain the max profit. For example, input -> [2,5,8,1,3,6,9,3,6], output -> [1,9]
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