old_contents: 
  //consice methods
  
  //the class
  
  //super
  
  //constructor
  
new_contents: 
  //consice methods and properties
  
  var z = 5, w = 10;
  
  var o = {
    x: function() {
      console.log('regular method');
    },
    
    y() {
      console.log('consice method');
    },
    
    z: z, //regular property
    w //consice property
  
  }
  
  //the class
  
  //super
  
  //constructor
  
subject: Update classes.js