Promises demo

promises.js

console.log("A");

var returnFromTwo = stepOne().then(stepTwo);

console.log("B");

returnFromTwo.then(stepThree);

console.log("C");


function stepOne(){

  console.log("running stepOne");

  return new Promise(function(resolve, reject){
    console.log("running stepOne Promise");

    setTimeout(_ => resolve("resolved stepOne"), 1000);
  });
}


function stepTwo(argToResolve){
  console.log("running stepTwo with arg: ", argToResolve);

  return new Promise(function(resolve, reject){
    console.log("running stepTwo Promise");
    setTimeout(_ => resolve("resolved stepTwo"), 5000);
  });
}

function stepThree(argToResolve){
  console.log("running stepThree ", argToResolve);
}

Output:

A
running stepOne
running stepOne Promise
B
C
running stepTwo with arg:  resolved stepOne
running stepTwo Promise
running stepThree  resolved stepTwo