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const kMeans = (data, k = 1) => {const centroids = data.slice(0, k);const distances = Array.from({ length: data.length }, () =>Array.from({ length: k }, () => 0));const classes = Array.from({ length: data.length }, () => -1);let itr = true;while (itr) {itr = false;for (let d in data) {for (let c = 0; c < k; c++) {distances[d][c] = Math.hypot(...Object.keys(data[0]).map(key => data[d][key] - centroids[c][key]));}const m = distances[d].indexOf(Math.min(...distances[d]));if (classes[d] !== m) itr = true;classes[d] = m;}for (let c = 0; c < k; c++) {centroids[c] = Array.from({ length: data[0].length }, () => 0);const size = data.reduce((acc, _, d) => {if (classes[d] === c) {acc++;for (let i in data[0]) centroids[c][i] += data[d][i];}return acc;}, 0);for (let i in data[0]) {centroids[c][i] = parseFloat(Number(centroids[c][i] / size).toFixed(2));}}}return classes;};kMeans([[0, 0], [0, 1], [1, 3], [2, 0]], 2); // [0, 1, 1, 0]
// promisify(f, true) to get array of resultsfunction promisify(f, manyArgs = false) {return function (...args) {return new Promise((resolve, reject) => {function callback(err, ...results) { // our custom callback for fif (err) {reject(err);} else {// resolve with all callback results if manyArgs is specifiedresolve(manyArgs ? results : results[0]);}}args.push(callback);f.call(this, ...args);});};}// usage:f = promisify(f, true);f(...).then(arrayOfResults => ..., err => ...);
const euclideanDistance = (a, b) =>Math.hypot(...Object.keys(a).map(k => b[k] - a[k]));euclideanDistance([1, 1], [2, 3]); // ~2.2361euclideanDistance([1, 1, 1], [2, 3, 2]); // ~2.4495
const MongoClient = require('mongodb').MongoClient;const assert = require('assert');// Connection URLconst url = 'mongodb://localhost:27017';// Database Nameconst dbName = 'myproject';// Use connect method to connect to the serverMongoClient.connect(url, function(err, client) {assert.equal(null, err);console.log("Connected successfully to server");const db = client.db(dbName);client.close();});
//Retries maxRetries number of times, meaning that if you have 0, then it'll run the function once.async function retryPromise(promiseFn, maxRetries = 3, delayOffset = 0, delayRandomRange = 0) {return new Promise((resolve, reject) => {promiseFn().then(resolve, (error) => { //On errorif (maxRetries <= 0) {return reject(error);} else {if(delayRandomRange * Math.random() + delayOffset < 1.0){return retryPromise(promiseFn, maxRetries - 1, delayOffset, delayRandomRange).then(resolve, reject);}else{return new Promise((resolveTwo, rejectTwo) => {setTimeout(() => {return retryPromise(promiseFn, maxRetries - 1, delayOffset, delayRandomRange).then(resolveTwo, rejectTwo);}, delayRandomRange * Math.random() + delayOffset);}).then(resolve, reject);}}});});}//Tests for that function.//Returns a function that will fail numTimes times, then will return aValuefunction functionThatReturnsAFunctionThatFailsACoupleTimes(numTimes, aValue){return async function(){if(numTimes == 0){return aValue;}numTimes--;throw false;};}const SMALL_NUMBER = 10;function testTest(failNumberOfTimes){let functionThatFailsACoupleTimes = functionThatReturnsAFunctionThatFailsACoupleTimes(failNumberOfTimes, true);//Test my testfor(let i = 0; i < (failNumberOfTimes * 2); ++i){function evalTest(val){let testTestFailedReason = "";if(val === undefined){testTestFailedReason = "Test test returned undefined for some reason.";}if((i + 1) > failNumberOfTimes){if(val === true){//We're good}else{testTestFailedReason = "Test test didn't return true when it should have.";}}else{if(val === false){//We're good}else{testTestFailedReason = "Test test didn't return false when it should have.";}}testTestFailedReason = testTestFailedReason || "Test test passed test case";console.log(testTestFailedReason, "at index", i, "where the function returned", val);}functionThatFailsACoupleTimes().then(evalTest, evalTest)};}testTest(SMALL_NUMBER);let testCaseCounter = 1;const throwsNoError = [(val)=>{if(val == true){console.log("Passed test case " + (testCaseCounter++));}else{console.error("Unexpected return value", val);}},()=>{console.error("It wasn't supposed to fail!")}]const throwsError = [(val)=>{console.error("It wasn't supposed to succeed!", val);},(val)=>{if(val == false){console.log("Passed test case " + (testCaseCounter++));}else{console.error("Unexpected return value", val);}}];//Runs SMALL_NUMBER times, because SMALL_NUMBER - 1 is the number of retries after the first onelet functionThatFailsACoupleTimes = functionThatReturnsAFunctionThatFailsACoupleTimes(SMALL_NUMBER - 1, true);retryPromise(functionThatFailsACoupleTimes, SMALL_NUMBER - 1).then(...throwsNoError)functionThatFailsACoupleTimes = functionThatReturnsAFunctionThatFailsACoupleTimes(SMALL_NUMBER - 1, true);//Runs SMALL_NUMBER - 1 times, because SMALL_NUMBER - 2 is the number of retries after the first oneretryPromise(functionThatFailsACoupleTimes, SMALL_NUMBER - 2).then(...throwsError)//Testing the delay. You'll have to wait a bit too.functionThatFailsACoupleTimes = functionThatReturnsAFunctionThatFailsACoupleTimes(SMALL_NUMBER - 1, true);//Runs SMALL_NUMBER times, because SMALL_NUMBER - 1 is the number of retries after the first oneretryPromise(functionThatFailsACoupleTimes, SMALL_NUMBER - 1, 500, 500).then(...throwsNoError)functionThatFailsACoupleTimes = functionThatReturnsAFunctionThatFailsACoupleTimes(SMALL_NUMBER - 1, true);//Runs SMALL_NUMBER - 1 times, because SMALL_NUMBER - 2 is the number of retries after the first oneretryPromise(functionThatFailsACoupleTimes, SMALL_NUMBER - 2, 500, 500).then(...throwsError)
// Vanilla JS Solution:var app = document.getElementById('app');var typewriter = new Typewriter(app, { loop: true });typewriter.typeString("I'm John and I'm a super cool web developer").pauseFor(3000).deleteChars(13) // "web developer" = 13 characters.typeString("person to talk with!") // Will display "I'm John and I'm a super cool person to talk with!".start();// React Solution:import Typewriter from 'typewriter-effect';<Typewriteroptions={{ loop: true }}onInit={typewriter => {typewriter.typeString("I'm John and I'm a super cool web developer").pauseFor(3000).deleteChars(13) // "web developer" = 13 characters.typeString("person to talk with!") // Will display "I'm John and I'm a super cool person to talk with!".start();}}/>