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/**
 * Returns a deep copy of the array or object passed to it.
 * Useful for copying objects and arrays with nested complex types.
 *
 * @param {array|object} o The value to deep copy, could be array or object.
 * @returns {array|object} Returns a deep copy of the supplied array or object.
 */
function deepClone(o) {
  // Construct the copy `output` array or object.
  // Use `Array.isArray()` to check if `o` is an array.

gladchinda

function isPalindrome(word) {
  return (
    !!(word && Object.prototype.toString.call(word) === '[object String]')
    && (
      word.length <= 1
      || RegExp(word[0], 'i').test(word.slice(-1))
      && isPalindrome(word.slice(1, -1))
    )
  )
}

gladchinda

// Create a new Express app and set the port
const app = require('express')();
const PORT = process.env.PORT || 5000;

// The timeout in seconds for API responses
const TIMEOUT_SECONDS = 5;

// Define a new route on the Express app: GET /random
app.get('/random', (req, res) => {
  

gladchinda

// An object that will contain the current temperatures of the cities
// The keys are the city names, while the values are their current temperatures (in °C)
let TEMPS = null;

// The maximum number of retries for failed temperature fetches
const MAX_TEMP_FETCH_RETRIES = 5;

/**
 * Fetches the current temperatures of multiple cities (in °C) and update the `TEMPS` object.
 * Also schedule retries for failed temperature fetches.

gladchinda

const fetchTempForCity = city => {
  return fetch(`${API_URL}&q=${encodeURIComponent(city)}`)
    .then(response => response.json())
    .then(data => [ city, data.main.temp || null ])
  
    // Attach a `.catch()` handler for graceful rejection handling
    .catch(() => [ city, null ]);
}

gladchinda

// Use your OpenWeatherMap API KEY
// Set the current weather data API URL
const API_KEY = 'YOUR_API_KEY_HERE';
const API_URL = `https://api.openweathermap.org/data/2.5/weather?appid=${API_KEY}&units=metric`;

// Set the list of cities
const CITIES = [
  'London', 'Tokyo', 'Melbourne', 'Vancouver',
  'Lagos', 'Berlin', 'Paris', 'Johannesburg',
  'Chicago', 'Mumbai', 'Cairo', 'Beijing'

gladchinda

const exchangeRate = currency => {
  const symbol = `${BASE_CURRENCY}_${currency}`;
  
  return fetch(`${API_URL}&q=${symbol}`)
    .then(response => response.json())
    .then(data => [ currency, data[symbol] || null ])
  
    // Attach a `.catch()` handler for graceful rejection handling
    .catch(() => [ currency, null ]);
}

gladchinda

// Use your CurrencyConverter API KEY
// Set the currency conversion API URL

const API_KEY = 'YOUR_API_KEY_HERE';
const API_URL = `https://free.currencyconverterapi.com/api/v6/convert?apiKey=${API_KEY}&compact=ultra`;

// Set the base currency (US Dollar in this case)
const BASE_CURRENCY = 'USD';

// Set the list of available currencies

gladchinda

const loadPhoto = photo_url =>
  new Promise(resolve => {
    const img = new Image();

    img.addEventListener('load', () => { 
      resolve(img);
    }, false);

    img.addEventListener('error', () => {
      const rejection = Promise.reject(new Error('Image could not be loaded.'));

gladchinda

/*******************************************************
 Avoid the following style definitions:
 - they are ignored by screen readers
 - they impact keyboard accessibility
 - they affect the visual flow of the page
 *******************************************************/

.hidden {
  display: none;
}