text: // demonstrating callbacks
  
  // this function accepts a callback
  function asyncFunc(callback) {
    // start a timer that will invoke the callback after 3000 ms (3 sec);
    setTimeout(callback, 3000);
  }
  
  // using this function as the callback for the above function
  function helloWorld() {
    console.log("hello, world");
  }
  
  // invoke the function, with the callback
  asyncFunc(helloWorld);
  
  