const numbers = [1, 2, 3, 4, 5];

const result = numbers
  .filter(n => n % 2 === 0)
  .map(n => n * 2)
  .reduce((acc, n) => acc + n, 0);

console.log(result);

var str="dog,cat,pig,cow"
var re1=/\b\w+\b/g
var re2=/\b\w+\b(?=,cat|,pig)/g   
var re3=/\b\w+\b(?!,cat|,pig)/g
var re4=/(?=c)\b\w+\b(?!,cat|,pig)/g  
console.log( str.match(re1))  
console.log( str.match(re2))  
console.log( str.match(re3))  
console.log( str.match(re4)) 

const person = {
  name: 'Alice',
  age: 25,
  city: 'Wonderland'
};

const additionalInfo = {
  age: 30,
  occupation: 'Explorer'
};

const combined = {
  ...person,
  ...additionalInfo
};

console.log(combined.age);

var str="abba baab green glass roof";
var reg=/(.)(.)\2\1/g
console.log( str.match(reg))

❓Что будет на выходе?

const a = async () => {
   return Promise.reject('Hello');
};

a().catch(error => console.log(error));
console.log('World');

❓Что будет на выходе?

function example() {
  console.log(a);
  var a = 10;
  console.log(a);
}
example();

❓Что будет на выходе?

var str="aaaabbbb";
console.log( str.match(/a{1}b{1}/)+"" );  
console.log( str.match(/a{2}b{2}/)+"" );  
console.log( str.match(/a{4}b{4}/)+"" ); 
console.log( str.match(/a{5}b{5}/)+"" );

function verify(username){
  return /^[a-z][a-z0-9_]{5,15}$/i.test(username);
}
console.log( verify("myjinxin2015"))  
console.log( verify("smile67"))       
console.log( verify("GiacomoSorbi"))  
console.log( verify("jhoffner"))      
console.log( verify("g964") )         
console.log( verify("matt c") )       /
console.log( verify("My_name_is_ZozoFouchtra") )

function addCommas(money){
  var re=/\d{3}/g
  return money.replace(re,x=>x+",")
}
console.log( addCommas("$123456789") )

function addCommas(money){
  var re=/\d{3}(?!$)/g
  return money.replace(re,x=>x+",")
}
console.log( addCommas("$123456789") )

const person = {
  firstName: 'John',
  lastName: 'Doe',
  age: 30,
  getFullName: function() {
    return this.firstName + ' ' + this.lastName;
  }
};

console.log(person.getFullName());

var str="javascript coffeescript vbscript javacode"
var re2=/(?=java)\b\w+script\b/g
console.log(str.match(re2))

var str="dog,cat,pig,cow"
var re2=/\b\w+\b(?=,cat|,pig)/g   
console.log(str.match(re2))

function addCommas(money){
  var re=/\d{3}(?!$)/g
  return money.replace(re,x=>x+",")
}
console.log( addCommas("$123456789") )  
console.log( addCommas("$123456") )    
console.log( addCommas("$1234567890") ) 
console.log( addCommas("$1234567") )

const a = '5';
const b = 5;
const c = 10;

const result1 = a == b;
const result2 = a === b;
const result3 = b < c;
const result4 = b >= c;

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

let a = 5;
let b = a++ + ++a;
console.log(b);

console.log(Math.round(1.45)); 
console.log(Math.ceil(1.45));  
console.log(Math.floor(1.45));
console.log(Math.round(1.55)); 
console.log(Math.ceil(1.55));  
console.log(Math.floor(1.55));

var str="example";
var result=str.replace("e","@");
console.log(result);

'use strict';

function strictModeExample() {
  undeclaredVariable = 10;
  try {
    console.log(undeclaredVariable);
  } catch (e) {
    console.log('Error:', e.message);
  }
}

strictModeExample();

let obj = { a: 1 };
Object.freeze(obj);

console.log(Object.isFrozen(obj));
console.log(obj.a = 2);
console.log(obj.a);

var str="My".concat("name","is","John");
console.log(str);

function* numberGenerator() {
  yield 1;
  yield 2;
  yield 3;
}

const gen = numberGenerator();
console.log(gen.next().value);
console.log(gen.next().value);
console.log(gen.next().value);
console.log(gen.next().value);