Check if array is empty
0 likes • Nov 19, 2022 • 0 views
JavaScript
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function formatDate(date) {return date.toLocaleDateString();}function Comment(props) {return (<div className="Comment"><div className="UserInfo"><imgclassName="Avatar"src={props.author.avatarUrl}alt={props.author.name}/><div className="UserInfo-name">{props.author.name}</div></div><div className="Comment-text">{props.text}</div><div className="Comment-date">{formatDate(props.date)}</div></div>);}const comment = {date: new Date(),text: 'I hope you enjoy learning React!',author: {name: 'Hello Kitty',avatarUrl: 'https://placekitten.com/g/64/64',},};ReactDOM.render(<Commentdate={comment.date}text={comment.text}author={comment.author}/>,document.getElementById('root'));
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 mongoose = require('mongoose')const UserSchema = new mongoose.Schema({username: {type: String,required: true},email: {type: String,unique: true,required: true},password: {type: String,required: true},date: {type: Date,default: Date.now}})module.exports = User = mongoose.model('user', UserSchema)
const flat = arr => [].concat.apply([], arr.map(a => Array.isArray(a) ? flat(a) : a));// Orconst flat = arr => arr.reduce((a, b) => Array.isArray(b) ? [...a, ...flat(b)] : [...a, b], []);// Or// See the browser compatibility at https://caniuse.com/#feat=array-flatconst flat = arr => arr.flat();// Exampleflat(['cat', ['lion', 'tiger']]); // ['cat', 'lion', 'tiger']
// 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 => ...);
var d = new Date();var d = new Date(milliseconds);var d = new Date(dateString);var d = new Date(year, month, day, hours, minutes, seconds, milliseconds);