Looking for an experienced NodeJS Developer

I am looking for an experienced NodeJS developer.
Salary is 5K monthly.
Include answers for below questions.

1) Convert the code below using any lib of your choice to be more readable
db.getData((err,data)=>{
 if(err){
  console.log(err)
  return
 }
 data.a = "test"
 data.b = 1111
 db.processData(data,(err,data)=>{
   if(err){
     console.log(err)
     return
 }
 db.saveData((err,data)=>{
  if(err){
   console.log(err)
   return
  }
  console.log("finished")
  })
 })
})


2) What is the output of this program and why?
let z = 4153000000000000000 + 99
console.log(z)