MERN Stack (Backend + Frontend Connection)

What does the mongod command do?

• A. Starts the MongoDB client shell to interact with databases

• B. Installs MongoDB on the system
  

• C. Starts the MongoDB server
  

• D. Creates a new MongoDB database with default settings

What does mongosh do?

• A. Starts the MongoDB server (the program that stores your data)
  

• B. Opens the MongoDB shell (a place where you can type commands to control the database)
  

• C. Installs MongoDB on your computer
  

• D. Deletes a database automatically

What does node server.js do?

• A. Starts the Node.js program and runs the code inside server.js
  

• B. Installs the Node.js server on your computer
  

• C. Opens a shell to write Node.js commands manually
  

• D. Deletes the server.js file and its folder

What does nodemon server.js do?

• A. Runs server.js one time using Node.js
  

• B. Automatically restarts server.js whenever you make changes to the file
  

• C. Deletes and recreates server.js repeatedly
  

• D. Opens a shell to manually run server.js commands

import React, { useState } from 'react';

import './App.css';

• A. It loads React and a CSS file to style the app, and lets you use the useState feature to manage data inside the app.
  

• B. It runs the app and applies all styles automatically.
  

• C. It connects the app to a database and imports the needed CSS from React itself.
  

• D. It exports the React app to the browser and saves the CSS file inside it.

function App() {

  const [formData, setFormData] = useState({ email: '', password: '' });

• A. It creates a state variable called formData with default empty values for email and password, and allows updating them using setFormData.
  

• B. It sends the email and password to the server automatically.
  

• C. It permanently stores email and password in the browser's storage.
  

• D. It deletes the email and password every time the page reloads.

const handleChange = (e) => {

    setFormData(prev => ({

      ...prev,

      [e.target.name]: e.target.value

    }));

  };

• A. It updates the specific field in formData when a form input changes, keeping the other fields unchanged.
  

• B. It resets all form fields to empty whenever any input is changed.
  

• C. It sends the entire form data to the server immediately after any input change.
  

• D. It deletes the form data whenever the input value is cleared.

const handleSubmit = async (e) => {

    e.preventDefault();

• A. It clears all inputs in the form.
  

• B. It stops the form from refreshing the page when submitted.
  

• C. It restarts the app whenever the form is submitted.
  

• D. It sends the form data to the server immediately.

try {

      const res = await fetch('http://localhost:5000/api/login', {

        method: 'POST',

        headers: { 'Content-Type': 'application/json' },

        body: JSON.stringify(formData)

      });

• A. It deletes data from the server at the given URL.
  

• B. It saves the formData to the user’s local storage automatically.
  

• C. It sends the formData as a JSON POST request to the specified server URL and waits for a response.
  

• D. It retrieves data from the server using a GET request.

const data = await res.json();

      alert(data.message);

    } catch (err) {

      console.error(err);

      alert('Error submitting form');

    }

  };

• A. It converts the server’s JSON response into a JavaScript object and shows a message from the response.
  

• B. It sends another request to the server automatically after the first one.
  

• C. It clears the form inputs if the response is successful.
  

• D. It restarts the app if there is an error during the request.