text: function fun() {
      console.log('This is a function.')
  }
  
  let fun2 = () => {
      console.log('fun2 function');
      return 'aaaa';
  };
  
  let fun3 = (a, b) => {
      console.log(a + b);
  };
  
  fun();
  fun2();
  
  fun3();
  fun3(20);
  fun3(10, 20);
  fun3('Sonu', ' Monu');
  fun3(5, 20, 30);
  
  
  
  // let SumAsync = (a,b) => {
  
  //     setTimeout(  () => {
  //         var result = a + b;
  //         return result;
  //     }, 1000);
  // }
  // console.log(SumAsync(4,2));
  
  // function logSum( result ){
  //     console.log( result );
  // }
  // console.log(SumAsync(1,2, logSum));
  
  
  let fun4 = (abc) => {
      setTimeout(() => {
         // callback({ message: 'fun message' });
          abc(10,20);
          
      }, 2000);
  }
  
  // simplified version 
  
  
  let someFunction = (a, b) => {
      console.log(a + b);
  }
  
  fun4(someFunction);
  
  // DOM 