async in js

async.js

function async(genFunc) {
    var gen = genFunc();
    function step(value) {
        var next = gen.next(value);
        var promise = next.value;
        return promise
            .then((v) => {
                if (!next.done) {
                    step(v);
                }
            })
            .catch((e) => gen.throw(e));
    }

    return step();
}

function delay(msg) {
  return new Promise(resolve=>{
     setTimeout(()=>{
        resolve(msg)
     },4000)
  })
}

//Promise 

function App(){
  Promise.resolve(delay('Babel !')).then((name)=>{
    console.log(`Hola ${name}`);
  })
}

App();

//Async-await

async function App_async(){
  let msg = await delay('Babel ! async');
  console.log(`Hola ${msg}`);  
}

App_async();

//Generators

function* App_gen(){
  let msg = yield delay('Babel ! generator');
  console.log(`Hola ${msg}`);   
}

async(App_gen);