NodeCodes

Welcome to the NodeCodes for learning!!

This repo is intended to provide beginner to intermediate level Node.js developers with a set of questions and answers that can help them improve their skills and knowledge of this JavaScript runtime environment. These are coding question generated by ChatGPT and I have written codes to these question as per my knowledge gained from reading docs on Node.js and the libraries and node packages.

Coding Question on Nodejs

1. Write a function in Node.js that reads a file named "data.txt" and logs its contents to the console
2. Write a function in Node.js that creates a new directory named "logs" and logs a message to a file named "info.log" inside the directory
3. Write a function in Node.js that fetches data from an API endpoint using the Axios library and returns the response
4. Write a function in Node.js that uses the native "http" module to create a simple HTTP server that listens on port 3000 and returns a "Hello, world!" message to any incoming request
5. Write a function in Node.js that accepts a command-line argument and logs it to the console
6. Write a function in Node.js that reads a CSV file named "data.csv" and converts its contents to JSON format
7. Write a function in Node.js that uses the "fs" module to recursively list all files and directories in a given directory
8. Write a function in Node.js that accepts a POST request containing JSON data and saves it to a file named "data.json"
9. Write a function in Node.js that uses the "crypto" module to generate a random 32-byte hexadecimal string
10. Write a function in Node.js that uses the "cluster" module to create a simple cluster of worker processes that each log a message to the console
11. Write a function that returns a Promise which resolves with a random number after a delay of 1 second
12. Write a function that returns a Promise which rejects with an error message after a delay of 500ms
13. Write a function that takes an array of numbers as input and returns a Promise which resolves with the sum of all the numbers in the array
14. Write a function that takes an array of Promises as input and returns a Promise which resolves with an array of resolved values from the input Promises
15. Write a function that fetches data from an API endpoint using the Axios library and returns a Promise which resolves with the response data. The function should reject the Promise if the API request fails

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1. Write a function in Node.js that reads a file named "data.txt" and logs its contents to the console

const fs = require('fs')

function logFileContent(){
    fs.readFile('./data.txt', 'utf-8' ,(err,data)=>{
        if(err) throw err;
        console.log(data);
    })
}

logFileContent();

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2. Write a function in Node.js that creates a new directory named "logs" and logs a message to a file named "info.log" inside the directory

const fs = require('fs');

function logToFile(){
    let myData = 'Logging to file info.log'
    fs.mkdir('./logs', { recursive: true }, (err) => {
        if(err) 
            throw err
        else {
            fs.writeFile('./logs/info.log', myData ,(err) => {
                if(err) throw err;
            });
        }
    });
    
}

logToFile();

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3. Write a function in Node.js that fetches data from an API endpoint using the Axios library and returns the response

const axios = require('axios');

async function fetchData(){
    try {
        const data = await axios.get('https://random-data-api.com/api/v2/users');
        return data;
    } catch (error) {
        throw error;
    }
}

fetchData()
.then(data => console.log(data.data))
.catch(error => console.log(error));

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4. Write a function in Node.js that uses the native "http" module to create a simple HTTP server that listens on port 3000 and returns a "Hello, world!" message to any incoming request.

const http = require('http');

http.createServer((req,res)=>{
  res.end('Hello World!!')
}).listen(3000);

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5. Write a function in Node.js that accepts a command-line argument and logs it to the console

function getArgs(){
    let args = process.argv.slice(2);
    console.log(args)
}

getArgs();

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6. Write a function in Node.js that reads a CSV file named "data.csv" and converts its contents to JSON format

const fs = require('fs').promises;

async function csvToJSON(){
    let data = await fs.readFile('./data.csv','utf8');
    let arr = data.split('\n');
    let json = [];
    let keys = arr[0].split(',');
    
    for(let i=1;i<arr.length;i++){
        let obj = {};
        let values = arr[i].split(',');
        
        for(let j=0;j<keys.length;j++){
            obj[keys[j]] = values[j];
        }

        json[i-1] = obj;

    }

    return JSON.stringify(json);
}

csvToJSON().then(data => console.log(data));

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7. Write a function in Node.js that uses the "fs" module to recursively list all files and directories in a given directory

const fs = require('fs');
const path = require('path');

function listFiles(){
    let directoryPath = '../'

    fs.readdir(directoryPath,(err,directories)=>{
        if(err) throw err;
        directories.forEach((directory)=>{
            fs.readdir(path.join(__dirname,'/..',directory),(err,files)=>{
                console.log('Directory: ', directory,'files: ',files);
            })
        })
    })
}

listFiles()

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8. Write a function in Node.js that accepts a POST request containing JSON data and saves it to a file named "data.json"

const http = require('http');
const fs = require('fs');

http.createServer((req,res)=>{
    if(req.method === 'POST' && req.url === '/'){
        req.on('data',(chunk)=>{
            fs.writeFile('./data.json',chunk,(err)=>{
                    if(err) throw err;
                })
        });

        res.end();
    }
}).listen(3000);

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9. Write a function in Node.js that uses the "crypto" module to generate a random 32-byte hexadecimal string

const crypto = require('crypto');

function getRandomHex(){
    let bytes = crypto.randomBytes(32).toString('hex');
    console.log(bytes);
}

getRandomHex();

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10. Write a function in Node.js that uses the "cluster" module to create a simple cluster of worker processes that each log a message to the console

const cluster  = require('cluster');
const { availableParallelism } = require('os');

const numCPUs = availableParallelism();

function generateClusters(){
    if(cluster.isPrimary){
        console.log("Primary Cluster: ", process.pid);

        for(let i=0;i<numCPUs;i++){
            let worker = cluster.fork();

            worker.on('online',()=>{
                console.log('Worker online: ', worker.process.pid);
            })
        }

    }
}

generateClusters();

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11. Write a function that returns a Promise which resolves with a random number after a delay of 1 second

function randomPromise(){
    let p = new Promise((resolve,reject)=>{
        setTimeout(() => {
            resolve(Math.floor(Math.random() * 100));
        }, 1000);
    })

    return p;
}

randomPromise().then(data=>console.log(data)); 

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12. Write a function that returns a Promise which rejects with an error message after a delay of 500ms

function rejectPromise(){
    let p = new Promise((resolve,reject)=>{
        setTimeout(() => {
            reject(new Error('Error Message'));
        }, 500);
    });

    return p;
}

rejectPromise().catch(err=>console.log(err));

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13. Write a function that takes an array of numbers as input and returns a Promise which resolves with the sum of all the numbers in the array

function sumArray(arr){
    let p = new Promise((resolve,reject)=>{
        let sum = arr.reduce((acc,current)=> acc+=current);
        resolve(sum);
    });

    return p;
}

sumArray([1,2,3,4]).then(data=>console.log(data));

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14. Write a function that takes an array of Promises as input and returns a Promise which resolves with an array of resolved values from the input Promises

function resolvePromise(p){
    return Promise.all(p)
}

let p1 = Promise.resolve(1);
let p2 = Promise.resolve(2);
let p3 = Promise.resolve(3);

resolvePromise([p1,p2,p3]).then(data=>console.log(data)).catch(err=>console.log(err));

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15. Write a function that fetches data from an API endpoint using the Axios library and returns a Promise which resolves with the response data. The function should reject the Promise if the API request fails

const axios = require('axios')

function fetchData(){
    return axios.get('https://random-data-api.com/api/v2/users')
        .then((data)=>data.data)
        .catch((error)=>error);
}

 fetchData().then(data=>console.log(data)).catch(err=>console.log(err));

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