ES6 async/await

async-await.js

// We can also use async/await which is a Syntactic Sugar For Promises
var addC = function (a, b) {
  return new Promise((resolve, reject) => {
    setTimeout (() => { 
      resolve(a + b); 
    }, 0);
  });
};


// your code using async functions is much more like using standard synchronous functions
// Note you should only use `await` inside a function that is declared as `async function`
async function main () {
  var r1 = await addC(1, 1);
  var r2 = await addC(r1, 1);
  var r3 = await addC(r2, 1);
  console.log(r3);
}
main();