text: /**
   * Arrays are used to store ordered collections.
   * 
   * Objects are for storing key:value collections.
   * With object we can't insert new property between existing ones.
   * 
   * An array can store elements of any type.
   */
  
  let vars = [
      "Apple", 
      "Orange", 
      () => {
          console.log('Hello World');
      },
      {name: 'John'}, // comma allowed
  ];
  console.log(vars[1]);       // Orange
  console.log(vars[3].name);  // John
  vars[2]();                  // Hello World
  
  
  /**
   * pop - extract last
   * push - append at the end of array
   * shift - extract first
   * unshift - add to begining of array
   * pop/push - also return the element
   */
  vars = ["Apple", "Orange"];
  
  vars.pop();
  console.log(vars); // [Apple]
  
  vars.push("Pear");
  console.log(vars); // [Apple, Pear]
  
  vars.shift();
  console.log(vars); // [Pear]
  
  vars.unshift("Orange", "Lemon");
  console.log(vars); // [Orange, Lemon, Pear]