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const geometricProgression = (end, start = 1, step = 2) =>Array.from({length: Math.floor(Math.log(end / start) / Math.log(step)) + 1,}).map((_, i) => start * step ** i);geometricProgression(256); // [1, 2, 4, 8, 16, 32, 64, 128, 256]geometricProgression(256, 3); // [3, 6, 12, 24, 48, 96, 192]geometricProgression(256, 1, 4); // [1, 4, 16, 64, 256]
const jwt = require("jsonwebtoken");const authToken = (req, res, next) => {const token = req.headers["x-auth-token"];try {req.user = jwt.verify(token, process.env.ACCESS_TOKEN_SECRET);next();} catch (err) {console.log(err.message);res.status(401).json({ msg: "Error authenticating token" });}};module.exports = authToken;
class SequentialQueue{ //if you want it to go backwards, too badnext(){return this.i++;}constructor(start = 0){this.i = start;}}const que = new SequentialQueue(0);for(let i = 0; i < 10; i++){console.log(que.next());}
class Timer{start(){this.startTime = Date.now();}stop(){const dt = Date.now() - this.startTime;console.log(dt);return dt;}getExecTime(fun, asynchronous){return asynchronous ? this.getAsyncExecTime(fun) : this.getSyncExecTime(fun);}getSyncExecTime(fun){this.start();fun();return this.stop();}async getAsyncExecTime(fun){this.start();await fun();return this.stop();}static average(fun, numTimes, asynchronous = false){const times = [];const promises = [];let timer = new Timer();if(asynchronous){for(let i = 0; i < numTimes; i++){timer.getAsyncExecTime(fun);}}else{for(let i = 0; i < numTimes; i++){timer.getSyncExecTime(fun);}}return (times => times.reduce(((sum, acc) => sume + acc), 0) / times.length);}static async timeAsync(fun, numTimes){if(numTimes <= 1) return new Timer().getAsyncExecTime(fun);const promises = [];let timer = new Timer(true);for(let i = 0; i < numTimes; i++){promises.push(fun().catch((e)=>{}));}try{await Promise.all(promises).catch((e)=>{});}catch(e){//do absolutely nothing}return timer.stop();}constructor(start = false){if(start) this.start();}}
const permutations = arr => {if (arr.length <= 2) return arr.length === 2 ? [arr, [arr[1], arr[0]]] : arr;return arr.reduce((acc, item, i) =>acc.concat(permutations([...arr.slice(0, i), ...arr.slice(i + 1)]).map(val => [item,...val,])),[]);};permutations([1, 33, 5]);// [ [1, 33, 5], [1, 5, 33], [33, 1, 5], [33, 5, 1], [5, 1, 33], [5, 33, 1] ]
const express = require('express')const app = express()const port = 3000app.get('/', (req, res) => {res.send('Hello World!')})app.listen(port, () => {console.log(`Example app listening on port ${port}`)})