What is the difference between callback and promise [duplicate]

Answer 1

Promises provide a more succinct and clear way of representing sequential asynchronous operations in javascript. They are effectively a different syntax for achieving the same effect as callbacks. The advantage is increased readability. Something like this

aAsync()
  .then(bAsync)
  .then(cAsync)
  .done(finish);

is much more readable then the equivalent of passing each of those individual functions as callbacks, like

Async(function(){
    return bAsync(function(){
        return cAsync(function(){
            finish()
        })
    })
});