Callback vs Promise and Async/Await

async-example.js

// Callback - Example:

// function to alert user name
var greeting = (name) => { alert('Hello ' + name); };

// function to process user input
var processUserInput = (callback) => { var name = prompt('Please enter your name.'); callback(name); };

// start call
processUserInput(greeting);



// Promise - Example:

// function to alert user name
var greeting = (name) => { alert('Hello ' + name); };

// function to process user input
var processUserInput = () => {
 return new Promise((resolve, reject) => {
	var name = prompt('Please enter your name.');
	if(name) resolve(name);
   	reject(false);
  });
};

// start call
processUserInput()
.then(result =>  greeting(result))


// Promise.all - Example:

var promise1 = Promise.resolve(3);
var promise2 = 42;
var promise3 =  new Promise((resolve, reject) => {
	setTimeout(resolve, 100, 'foo');
});

Promise.all([promise1, promise2, promise3])
.then(result =>  console.log(result))


// Promise.race - Example:

var promise1 = Promise.resolve(3);
var promise2 = 42;
var promise3 =  new Promise((resolve, reject) => {
	setTimeout(resolve, 100, 'large');
});

var promise4 =  new Promise((resolve, reject) => {
	setTimeout(resolve, 10, 'small');
});

Promise.race([promise3, promise4])
.then(result =>  console.log(result))


// Async/Await - Example:

// function to alert user name
var greeting = (name) => { alert('Hello ' + name); };

// function to process user input
var processUserInput = () => {
 return new Promise((resolve, reject) => {
	var name = prompt('Please enter your name.');
	if(name) resolve(name);
   	reject(false);
  });
};

//The word “async” before a function means one simple thing: a function always returns a promise.
async function asyncCall() {
  //The keyword await makes JavaScript wait until that promise settles and returns its result.
  var result = await processUserInput();
  // expected output: "resolved"
  greeting(result)
}

// start call
asyncCall();

Very Informative :) Thanks