async using callback

async-callback.js

// Async using call back
var addA = function (a, b, cb) {
  setTimeout (() => {
    cb(a + b);
  }, 0);
};

// How to use it :D
addA(2, 3, (result) => {
  console.log(result)
})

// Callback Hell :(
addA(1, 1, (r) => {
  addA(r, 1, (r) => {
    addA(r, 1, (r) => {
      addA(r, 1, (r) => {
        addA(r, 3, (r) => {
          addA(r, 3, (r) => {
            console.log(r)
          })
        })
      })
    })
  })
})