text: function sum(num1, num2){
      return num1 + num2;
  }
  
  function calc(num1, num2, callback){
      return callback(num1, num2);
  } 
  
  console.log(calc(6, 2, sum));
  
  function date(callback){
      console.log(new Date);
      setTimeout(function(){
          let date = new Date;
          callback(date);
      }, 3000)
  }
  
  function printDate(dateNow){
      console.log(dateNow);
  }
  
  date(printDate);