array shuffle
0 likes • Nov 19, 2022
JavaScript
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const nums = [1, 2, 3];const strs = Array.from('est');nums.push(6);nums.push(4, 9);strs.unshift('t');nums.length; // 6nums[nums.length - 1]; // 9strs[0]; // 't'strs[2]; // 's'nums.slice(1, 3); // [2, 3]nums.map(n => n * 2); // [2, 4, 6, 12, 8, 18]nums.filter(n => n % 2 === 0); // [2, 6, 4]nums.reduce((a, n) => a + n, 0); // 25strs.reverse(); // ['t', 's', 'e', 't']strs.join(''); // 'test'const nums = new Set([1, 2, 3]);nums.add(4);nums.add(1);nums.add(5);nums.add(4);nums.size; // 5nums.has(4); // truenums.delete(4);nums.has(4); // false[...nums]; // [1, 2, 3, 5]nums.clear();nums.size; // 0const items = new Map([[1, { name: 'John' }],[2, { name: 'Mary' }]]);items.set(4, { name: 'Alan' });items.set(2, { name: 'Jeff' });items.size; // 3items.has(4); // trueitems.get(2); // { name: 'Jeff' }items.delete(2);items.size; // 2[...items.keys()]; // [1, 4][...items.values()]; // [{ name: 'John' }, { name: 'Alan' }]items.clear();items.size; // 0
import React, { useState } from 'react' import Welcome from '../components/Welcome' function About() { const [showWelcome, setShowWelcome] = useState(false) return ( <div> {showWelcome ? <Welcome /> : null} </div> <div> {showWelcome && <Welcome /> } </div> ) } export default App
router.post("/", async (req, res) => {const { email, password } = req.body;try {if (!email) return res.status(400).json({ msg: "An email is required" });if (!password)return res.status(400).json({ msg: "A password is required" });const user = await User.findOne({ email }).select("_id password");if (!user) return res.status(400).json({ msg: "Invalid credentials" });const match = await bcrypt.compare(password, user.password);if (!match) return res.status(400).json({ msg: "Invalid credentials" });const accessToken = genAccessToken({ id: user._id });const refreshToken = genRefreshToken({ id: user._id });res.cookie("token", refreshToken, {expires: new Date(Date.now() + 604800),httpOnly: true,});res.json({ accessToken });} catch (err) {console.log(err.message);res.status(500).json({ msg: "Error logging in user" });}});
const linearSearch = (arr, item) => {for (const i in arr) {if (arr[i] === item) return +i;}return -1;};linearSearch([2, 9, 9], 9); // 1linearSearch([2, 9, 9], 7); // -1
const kNearestNeighbors = (data, labels, point, k = 3) => {const kNearest = data.map((el, i) => ({dist: Math.hypot(...Object.keys(el).map(key => point[key] - el[key])),label: labels[i]})).sort((a, b) => a.dist - b.dist).slice(0, k);return kNearest.reduce((acc, { label }, i) => {acc.classCounts[label] =Object.keys(acc.classCounts).indexOf(label) !== -1? acc.classCounts[label] + 1: 1;if (acc.classCounts[label] > acc.topClassCount) {acc.topClassCount = acc.classCounts[label];acc.topClass = label;}return acc;},{classCounts: {},topClass: kNearest[0].label,topClassCount: 0}).topClass;};const data = [[0, 0], [0, 1], [1, 3], [2, 0]];const labels = [0, 1, 1, 0];kNearestNeighbors(data, labels, [1, 2], 2); // 1kNearestNeighbors(data, labels, [1, 0], 2); // 0
const unzipWith = (arr, fn) =>arr.reduce((acc, val) => (val.forEach((v, i) => acc[i].push(v)), acc),Array.from({length: Math.max(...arr.map(x => x.length))}).map(x => [])).map(val => fn(...val));unzipWith([[1, 10, 100],[2, 20, 200],],(...args) => args.reduce((acc, v) => acc + v, 0));// [3, 30, 300]