Candidates Exam – Node.js + Vue.js

Section 1: Node.js

Implement logging and exception handling mechanism in Node JS core, use well known concepts and design patterns

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Consider the following Node.js code snippet that uses Sequelize for interacting with a database. The code is intended to create a User model and insert a new user into the database. However, there might be some issues and areas for improvement:

// models/User.js

const { DataTypes } = require('sequelize');

const sequelize = require('../config/database');

const User = sequelize.define('User', {

username: {

type: DataTypes.STRING,

allowNull: false,

},

email: {

type: DataTypes.STRING,

allowNull: false,

},

});

module.exports = User;

// controllers/userController.js

const User = require('../models/User');

async function createUser(username, email) {

try {

const user = await User.create({

username: username,

email: email,

});

console.log('User created successfully:', user);

} catch (error) {

console.error('Error creating user:', error);

}

}

createUser('john_doe', '[e-mail]');

● Identify potential issues in the provided code and explain them.

● Propose improvements to address the identified issues and optimize the code.

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Given the code below, after deployment, QA reports slowness in showing large data.

a. Explain the possible reasons for the slowness

b. Introduce code improvements to improve performance.

const fetchData = async () => {

const data = await database.query('SELECT * FROM large_data_set');

// Process the data, which may involve synchronous operations

const processedData = process(data);

return processedData;

};

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Section 2: Vue

State Management, Create a Vue component for a dynamic form where the number of input fields can be increased by the user. Manage the state of all input fields using a single-state object.

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Develop a Vue service that performs HTTP requests to a public API (like a weather API or a public JSON placeholder API).

Then, create a component that uses this service to fetch data and display it in a formatted way.

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Using Vue, Implement a simple Observable that emits values over time (like a counter).
Then, create a component that subscribes to this Observable and displays its values in real time.

Additionally, include a way to unsubscribe from the Observable to demonstrate good practice in managing subscriptions.

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Section 3: General Development

7

Write a function in (in any code) that finds the factorial of a given integer using recursion.

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Given a sorted array from 1 to N, there is a bug that somewhere in the array there is a “jump” of 1 number, Write an algorithm in Node/Vue JS to find the index of the “jump”, consider time and place complexity, assume you don’t know the size of the array and it can be very large.

Example:

index 0 1 2 3 4 5 6 7 8 9

value 0 1 2 3 5 6 7 8 9 10

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Write a SQL query to retrieve all unique customers who have made purchases in the last month from a "Customers" table and an "Orders" table.

Assume you have a "Customers" table with a unique "CustomerID" and an "Orders" table with a "CustomerID" and a "OrderDate" column.

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