text: var country1 = "Russia";
  var country2 = "USA";
  var country3 = "China";
  var countries = ["Russia", "USA", "China"];
  
  countries[0];
  countries[1];
  
  countries[2] = "France";
  countries;
  
  var mixed = [true, 20, "string"];
  mixed.length;
  
  // pop()
  var myArr = ["one", "two", "three"];
  var lastItem = myArr.pop(); // "three"
  myArr; // ["one", "two"]
  
  // push()
  myArr.push("new_item");
  myArr; // ["one", "two", "new_item"]
  
  myArr[myArr.length - 1];
  
  // Nested arrays
  var matrix = [[1, 2, 3], [4, 5, 6], [7, 8, 9]];
  
  // Array iteration
  var arr = ["A", "B", "C"];
  for(var i = 0; i < arr.length; i++){
      console.log(arr[i]);
  }
  
  for (letter of arr){
      console.log(letter);
  }
  
  for (letter of arr){
      alert(letter);
  }
  
  arr.forEach(alert);
  
  function addAwesome(name) {
      console.log(name + " is awesome!");
  }
  
  var topics = ["python", "django", "science"];
  topics.forEach(addAwesome);
  