How to differentiate exceptions from rejections

exceptionsAndPromises.js

// 1. Using rejections for both exceptions and rejections
foo(5)
  .then(bar)
  .catch(err => {
    if (!(err instanceof MyError)) {{
      // exception!
      throw err
    }
    // else, process business logic error properly
  })
  
// 2. Using data.Task
//  Exceptions will throw and task will never reject nor resolve
foo(5)
  .fork(err => {
    // business logic error
  }, bar)

// 3. Returning errors inside a resolve
foo(5)
  .then(bar => {
    if (bar instanceof MyError) {
      // handle business logic error
      return
    }
  // ...
  })
  .catch(err => {
    // handle exception
  })

Gleb Bahmutov Mod Gunar C. Gessner • 2 hours ago

I rarely try to handle specific errors by looking at the error class or information.
Instead I prefer to deal with just the fact that something has not happened.
For example, if I wanted to create a file and there was an error, I might print it, but not try to
look at the reason ("out of space" - nothing I can do, "busy" - retry again)