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Node.js Essentials

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Addition Function const result = Number(process.argv[2]) + Number(process.argv[3]); console.log(result); Working with Timers#1 setInterval(() => {console.log('TCS');}, 5000); Working with Timers#2 setTimeout(() => {console.log('TCS');}, 2000); Working with Timers#3 const interval = setInterval(() => { console.log('TCS'); }, 2000); setTimeout(() => { clearInterval(interval); }, 10000); Working with callback functions let sum = 0; for(let i=0; i<=1000; i++) { if( i % 3 == 0 ){ sum = sum + i; } } for(let i=0; i<=1000; i++) { if( i % 5 == 0 ){ sum = sum + i; } } console.log(sum); read Stream const fs = require("fs"); var data = ""; const src = fs.createReadStream('Node-stream-handson/data_file.txt', 'utf8'); src.on('data', chunk => { console.log(chunk.length); } ); copy stream const fs = require("fs"); const src = fs.createReadStream('data_file.txt', 'utf8'); src.pipe( fs.createWriteStream('new_data_file.txt') ); Explore Modules var module = require('./module'); var App = require('./App'); const readline = require('readline'); const rs = fs.createReadStream('./input.csv'); //writestreamを作成 const ws = fs.createWriteStream('./output.csv'); const rl = readline.createInterface({ //読み込みたいストリームの設定 input: rs, //書き出したいストリームの設定 output: ws }); Events - file systems const fs = require("fs"); fs.mkdir('Node_folder', (err) => { if (err) { throw err; } console.log('testディレクトリが作成されました'); }); // 書き込むデータ準備 const data = "This is Node.js a powerful backend javascript used very widely in industry for developing web applications."; // 書き込み fs.writeFile("Node_folder/sample.txt", data, (err) => { if (err) throw err; console.log('正常に書き込みが完了しました'); }); Events - http module var http = require('http'); var server = http.createServer(function(request, response) { response.writeHead(200, {'Content-Type': 'text/html; charset=utf-8'}); response.end('Hello world'); }) App build - Server Setup var http = require('http'); var html = require('fs').readFileSync('Sample.html'); var server = http.createServer(function(request, response) { response.writeHead(200, {'Content-Type': 'text/html'}); response.end('Hello World'); }) server.listen(8000); App build - Routing const http = require('http'); var url = require('url'); const server = http.createServer((req, res) => { var pathname = url.parse(request.url).pathname; if( pathname == '/hi' ){ res.writeHead(200, { 'Content-Type': 'text/html; charset=utf-8' }); res.write('Hi Welcome'); res.end(); } else if( pathname == '/hello' ) { res.writeHead(200, { 'Content-Type': 'text/html; charset=utf-8' }); res.write('Hello Buddy'); res.end(); } else { res.writeHead(404, { 'Content-Type': 'text/html; charset=utf-8' }); res.write('404 Page not Found'); res.end(); } }); const port = 8000; server.listen(port); App build - Routing2 const http = require('http'); var url = require('url'); const server = http.createServer((req, res) => { var pathname = url.parse(request.url).pathname; if( pathname == '/hi' ){ res.writeHead(200, { 'Content-Type': 'text/html; charset=utf-8' }); res.write('Hi Welcome'); res.end(); } else if( pathname == '/hello' ) { res.writeHead(200, { 'Content-Type': 'text/html; charset=utf-8' }); res.write('Hello Buddy'); res.end(); } else { res.writeHead(404, { 'Content-Type': 'text/html; charset=utf-8' }); res.write('404 File not found error'); res.end(); } }); const port = 8000; server.listen(port); App build - Posting Data const http = require('http'); var url = require('url'); const server = http.createServer((req, res) => { var pathname = url.parse(request.url).pathname; if (pathname == '/hi') { res.writeHead(200, { 'Content-Type': 'text/html; charset=utf-8' }); res.write('Hi Welcome'); res.end(); } else if (pathname == '/hello') { res.writeHead(200, { 'Content-Type': 'text/html; charset=utf-8' }); res.write('Hello Buddy'); res.end(); } else { res.writeHead(404, { 'Content-Type': 'text/html; charset=utf-8' }); res.write('404 Page not Found'); res.end(); } }); const port = 8000; server.listen(port); var http = require('http'); const querystring = require('querystring'); http .createServer(function (req, res) { if (req.method === 'POST') { res.writeHead(200, { 'Content-Type': 'text/html' }); var data = ''; //POSTデータを受けとる req .on('data', (chunk) => { data += chunk; }) .on('end', () => { var form = querystring.parse(data); res.end(form); }); } }) .listen(8000); App build - Handling Requests var server = require('./server.js'); var routers = require('./routers.js'); var handlers = require('./handlers.js'); App build - https request // App const https = require('https'); const fs = require('fs'); const options = { hostname: 'en.wikipedia.org', port: 443, path: '/wiki/Nodejs', method: 'GET', }; https .get(options, (resp) => { let data = ''; // A chunk of data has been received. resp.on('data', (chunk) => { data += chunk; }); // The whole response has been received. Print out the result. resp.on('end', () => { fs.writeFile('Nodejs.html', data, (err) => {console.log(err)}); }); }) .on('error', (err) => { console.log('Error: ' + err.message); }); Events - Working with Custom Events var events = require('events'); var eventEmitter = new events.EventEmitter(); //Create an event handler: var Myfunc = function () { console.log('HI THERE ! HAPPY LEARNING'); } eventEmitter.on('MyEvent', Myfunc); eventEmitter.emit('MyEvent'); Events - http module var http = require('http'); var html = require('fs').readFileSync('Sample.html'); var server = http.createServer(function(request, response) { response.writeHead(200, {'Content-Type': 'text/html'}); response.end(html); }) server.listen(8000); ======================== <!DOCTYPE html> Welcome ! what would you like to have Coffee Tea Milk Read Stream var fs = require('fs'); var stream; readerStream = fs.createReadStream('data_file.txt'); readerStream.setEncoding('UTF8'); readerStream.on('data', (chunk) => { console.log(chunk.length); }); Palindrome function largestPalindrome() { var arr = []; for (var i = 999; i > 100; i--) { for (var j = 999; j > 100; j--) { var mul = j * i; if (isPalin(mul)) { arr.push(j * i); } } } return Math.max.apply(Math, arr); } function isPalin(i) { return i.toString() == i.toString().split('').reverse().join(''); } console.log(largestPalindrome()); Evenly divisible number function findFactor(n, max) { for (let i = 2; i <= max; i++) { if (n % i !== 0) return false; } return true; } let n = 20; //measuring performance for (let i = n; true; i += n) { if (findFactor(i, n)) { console.log(i); break; } else if (i > 1e10) { console.log('Limit'); break; } } Fibonacci Series\ function sumFibs(num) { let previous = 0; let current = 1; let sum = 0; let next; for(current; current <= num;){ next = current + previous; previous = current; if(current % 2 === 0) { sum += current; } current = next; } return sum; } console.log(sumFibs(4000000)); // return 4613732 largest prime factor var divisor = 2; var number = 600851475143; while(number > 1){ if(number % divisor === 0){ number /= divisor; } else { divisor++; } } console.log(divisor); // the largest prime factor of 600851475143 Sum of Squares const sumSquareDifference = (n) => { const numbers = [...Array(n + 1).keys()]; const sumOfSquares = numbers.reduce( (accumulator, number) => accumulator + number ** 2 ); const squareOfSum = numbers.reduce((accumulator, number) => accumulator + number) ** 2; return squareOfSum - sumOfSquares; }; console.log(sumSquareDifference(100)); nth prime number function getPrimes(max) { let arr = new Array(max).fill(undefined); for (let i = 2; i < max; i++) { if (arr[i] === undefined) { arr[i] = true; for (let j = i + i; j < max; j += i) { arr[j] = false; } } } return arr.map((item, i) => (item ? i : false)).filter(Boolean); } let primes = getPrimes(150000); console.log(primes[10000]); Pythogorean triplet for (var a = 1; a < 500; a++) { for (var b = a; b < 1000; b++) { var c = Math.sqrt(a * a + b * b); if (c > b && Number.isInteger(c) && a + b + c == 1000) { console.log(a * b * c); } } } ============================= function isPrime(val){ //test if number is prime for(var i=2; i < val; i++){ if(val % i === 0){ return false; } } return true; } sum Primes function sumPrimes(num) { let arr = Array.from({length: num+1}, (v, k) => k).slice(2); let onlyPrimes = arr.filter( (n) => { let m = n-1; while (m > 1 && m >= Math.sqrt(n)) { if ((n % m) === 0) return false; m--; } return true; }); return onlyPrimes.reduce((a,b) => a+b); } Sum of Multiples let sum = 0; // loop max range const numRange = 1000; // common util function for checking multiples const isMultiple = (num, mode) => (num % mode ? false : true); // looping over an numbers below 1000 and adding 3 or 5 // multiples to sum for (let i = 0; i < numRange; i++) { if (isMultiple(i, 3) || isMultiple(i, 5)) sum += i; } // logs the sum of all the multiples of // 3 or 5 below 1000 => 233168 console.log(sum); console.log(sumPrimes(5)); sum Prime function sumPrime(x) { var array = [], sum=0; for (var i=2; i<x; i++) { if(typeof array[i] === 'undefined') { array[i]=true; for(var k = i+i; k<x; k+=i) { array[k]=false; } if (array[i]) { sum+=i; } } } return sum; } console.log(sumPrime(2000000)); // 142913828922

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