2-callbacks.js

//Callbacks are the foundation of Node.js
//A callback is a function called at the completion of a given task;
//This prevents any blocking, and allows other code to be run in the meantime.

const doWorkCallback = callback => {
  setTimeout(() => {
    callback("This is an error!", undefined);
    //callback(undefined, [1,2,3])
  }, 2000);
};

doWorkCallback((error, result) => {
  if (error) {
    return console.log(error);
  }
  console.log(result);
});

//Previous Sintaxe

function myFunction(myCallback) {
  setTimeout(function anotherFunction() {
    //callback('This is an error!', undefined)
    myCallback("error", undefined);
  }, 2000);
}

myFunction(function oneMoreFunction(error, result) {
  if (error) {
    return console.log(error);
  }
  console.log(result);
});