const obj = {
  name: 'Sarah',
  regularMethod: function() {
    return () => {
      console.log(this.name);
    };
  },
  arrowMethod: () => {
    return () => {
      console.log(this.name);
    };
  }
};

const regular = obj.regularMethod();
const arrow = obj.arrowMethod();
regular();
arrow();

console.log('1');
setTimeout(() => console.log('2'), 0);
Promise.resolve().then(() => console.log('3'));
setTimeout(() => console.log('4'), 0);
console.log('5');
Promise.resolve().then(() => {
  console.log('6');
  return Promise.resolve();
}).then(() => console.log('7'));
queueMicrotask(() => console.log('8'));
console.log('9');

class EventManager {
  constructor() {
    this.listeners = new Map();
  }
  
  addListener(event, callback) {
    if (!this.listeners.has(event)) {
      this.listeners.set(event, new Set());
    }
    this.listeners.get(event).add(callback);
  }
}

const manager = new EventManager();
const obj = { name: 'Component' };
manager.addListener('click', () => console.log(obj.name));
obj = null;
console.log(manager.listeners.get('click').size);

const multiply = (a) => (b) => (c) => a * b * c;

const step1 = multiply(2);
const step2 = step1(3);
const result1 = step2(4);

const result2 = multiply(2)(3)(4);

const partialMultiply = multiply(5);
const result3 = partialMultiply(2)(3);

const doubler = multiply(2)(1);
const result4 = doubler(7);

console.log(result1, result2, result3, result4);

const moduleCache = new Map();

async function loadModule(name) {
  if (moduleCache.has(name)) {
    return moduleCache.get(name);
  }
  
  const module = await Promise.resolve({
    default: () => `Module ${name} loaded`,
    version: '1.0.0'
  });
  
  moduleCache.set(name, module);
  return module;
}

const results = [];
loadModule('auth').then(m => results.push(m.default()));
loadModule('auth').then(m => results.push(m.version));
loadModule('utils').then(m => results.push(m.default()));

setTimeout(() => console.log(results.join(', ')), 0);

const nums = [1, 2, 3, 4, 5];
const result = nums
  .filter(n => n > 2)
  .map(n => n * 2)
  .reduce((acc, n) => {
    acc.push(n + 1);
    return acc;
  }, [])
  .slice(1);

console.log(result);
console.log(nums);

const cache = new Map();

function createHandler(id) {
  const data = { id, value: new Array(1000).fill(id) };
  cache.set(id, data);
  
  return function(action) {
    if (action === 'get') return data;
    if (action === 'clear') cache.delete(id);
  };
}

const handler1 = createHandler('user-1');
const handler2 = createHandler('user-2');

handler1('clear');
console.log(cache.size);
console.log(handler1('get').id);