CODE EXAMPLE FOR JAVASCRIPT

faker js

function doA(cb) { console.log('doA'); setTimeout(cb); }
function doB() { console.log('doB'); }
function doC(cb) { console.log('doC'); setTimeout(cb); }
function doD() { console.log('doD'); }
function doE() { console.log('doE'); }
function doF(cb) { console.log('doF');}

doA(function(){
  doB();
  doC(function() {
    doD();
  })
  doE();
});
doF();
 Run code snippet